Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 09, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	MD
Entity Registrant Name	MEDNAX, INC.
Entity Central Index Key	0000893949
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		93,795,535
Entity Public Float			$ 4,785,069,881

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 60,200	$ 55,698
Short-term investments	10,292	11,286
Accounts receivable, net	503,999	495,276
Prepaid expenses	15,584	11,051
Other assets	37,160	13,817
Total current assets	627,235	587,128
Restricted cash	20,000
Investments	80,682	78,975
Property and equipment, net	123,536	103,068
Goodwill	4,283,963	3,845,157
Intangible assets, net	639,928	668,529
Other assets	91,934	56,543
Total assets	5,867,278	5,339,400
Current liabilities:
Accounts payable and accrued expenses	438,017	407,938
Current portion of long-term debt and capital lease obligations	1,401	22,054
Income taxes payable	92,007	18,957
Total current liabilities	531,425	448,949
Line of credit	1,110,500	783,500
Long-term debt and capital lease obligations, net	740,923	900,128
Long-term professional liabilities	212,274	173,080
Deferred income taxes	147,797	227,802
Other liabilities	57,905	45,174
Total liabilities	2,800,824	2,578,633
Commitments and contingencies
Shareholders' equity:
Preferred stock; $.01 par value; 1,000 shares authorized; none issued
Common stock; $.01 par value; 200,000 shares authorized; 93,721 and 93,718 shares issued and outstanding, respectively	937	937
Additional paid-in capital	1,017,328	974,304
Retained earnings	2,048,189	1,785,526
Total shareholders' equity	3,066,454	2,760,767
Total liabilities and shareholders' equity	$ 5,867,278	$ 5,339,400

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	93,721,000	93,718,000
Common stock, shares outstanding	93,721,000	93,718,000

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net revenue	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 830,770	$ 828,006	$ 771,759	$ 752,624	$ 3,458,312	$ 3,183,159	$ 2,779,996
Operating expenses:
Practice salaries and benefits	617,455	586,476	561,418	572,385	532,952	521,832	484,625	491,811	2,337,734	2,031,220	1,753,505
Practice supplies and other operating expenses	32,353	29,497	30,872	27,796	32,737	31,641	26,992	27,046	120,518	118,416	98,480
General and administrative expenses	108,895	101,430	103,015	103,765	97,049	93,457	92,116	89,950	417,105	372,572	305,915
Depreciation and amortization	26,414	25,116	25,735	25,614	25,254	24,185	20,241	19,584	102,879	89,264	64,228
Total operating expenses	785,117	742,519	721,040	729,560	687,992	671,115	623,974	628,391	2,978,236	2,611,472	2,222,128
Income from operations	125,703	126,432	121,904	106,037	142,778	156,891	147,785	124,233	480,076	571,687	557,868
Investment and other income	2,777	235	365	576	770	221	410	618	3,953	2,019	1,844
Interest expense	(19,844)	(18,428)	(18,535)	(17,752)	(16,356)	(17,215)	(15,058)	(14,463)	(74,559)	(63,092)	(23,110)
Equity in earnings of unconsolidated affiliates	(294)	(240)	689	797	806	796	789	794	952	3,185	3,127
Total non-operating expenses	(17,361)	(18,433)	(17,481)	(16,379)	(14,780)	(16,198)	(13,859)	(13,051)	(69,654)	(57,888)	(18,139)
Income before income taxes	108,342	107,999	104,423	89,658	127,998	140,693	133,926	111,182	410,422	513,799	539,729
Income tax provision	27,761	(42,119)	(40,725)	(34,967)	(49,919)	(44,272)	(51,601)	(43,411)	(90,050)	(189,203)	(204,038)
Net income					78,079	96,421	82,325	67,771	320,372	324,596	335,691
Net loss attributable to noncontrolling interests						88	102	128		318	629
Net income attributable to MEDNAX, Inc.	$ 136,103	$ 65,880	$ 63,698	$ 54,691	$ 78,079	$ 96,509	$ 82,427	$ 67,899	$ 320,372	$ 324,914	$ 336,320
Net income attributable to MEDNAX, Inc.:
Earnings per share, Basic	$ 1.47	$ 0.71	$ 0.69	$ 0.59	$ 0.84	$ 1.04	$ 0.89	$ 0.74	$ 3.47	$ 3.52	$ 3.61
Earnings per share, Diluted	$ 1.46	$ 0.71	$ 0.69	$ 0.59	$ 0.84	$ 1.04	$ 0.89	$ 0.73	$ 3.45	$ 3.49	$ 3.58
Weighted average common shares:
Basic	92,756	92,589	92,181	92,360	92,728	92,604	92,182	92,269	92,431	92,422	93,077
Diluted	93,159	92,881	92,812	93,143	93,347	93,146	92,945	93,091	92,958	93,109	93,960

Consolidated Statements of Equity - USD ($) shares in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2014	$ 2,265,566,000	$ 960,000	$ 886,877,000	$ 1,376,782,000	$ 947,000
Balance, Shares at Dec. 31, 2014		96,030
Net income (loss)	335,691,000			336,320,000	(629,000)
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan	20,128,000	$ 5,000	20,123,000
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares		463
Issuance of restricted stock and vesting of deferred stock		$ 5,000	(5,000)
Issuance of restricted stock and vesting of deferred stock, shares		527
Issuance of restricted stock for acquisition consideration	7,800,000	$ 1,000	7,799,000
Issuance of restricted stock for acquisition consideration, shares		114
Stock-based compensation expense	32,129,000		32,129,000
Forfeitures of restricted stock, shares		(30)
Repurchased common stock	(235,051,000)	$ (34,000)	(32,271,000)	(202,746,000)
Repurchased common stock, shares		(3,365)
Excess tax benefit related to employee stock incentive plans	11,583,000		11,583,000
Balance at Dec. 31, 2015	2,437,846,000	$ 937,000	926,235,000	1,510,356,000	318,000
Balance, Shares at Dec. 31, 2015		93,739
Net income (loss)	324,596,000			324,914,000	$ (318,000)
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan	22,022,000	$ 5,000	22,017,000
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares		473
Issuance of restricted stock		$ 5,000	(5,000)
Issuance of restricted stock, shares		505
Stock-based compensation expense	34,000,000		34,000,000
Forfeitures of restricted stock		$ (1,000)	1,000
Forfeitures of restricted stock, shares		(53)
Repurchased common stock	(61,828,000)	$ (9,000)	(12,075,000)	(49,744,000)
Repurchased common stock, shares		(946)
Excess tax benefit related to employee stock incentive plans	4,131,000		4,131,000
Balance at Dec. 31, 2016	2,760,767,000	$ 937,000	974,304,000	1,785,526,000
Balance, Shares at Dec. 31, 2016		93,718
Net income (loss)	320,372,000			320,372,000
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan	23,276,000	$ 5,000	23,271,000
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares		528
Issuance of restricted stock		$ 5,000	(5,000)
Issuance of restricted stock, shares		536
Issuance of restricted stock for acquisition consideration	2,658,000	$ 1,000	2,657,000
Issuance of restricted stock for acquisition consideration, shares		69
Stock-based compensation expense	29,573,000		29,573,000
Forfeitures of restricted stock		$ (1,000)	1,000
Forfeitures of restricted stock, shares		(92)
Repurchased common stock	(70,192,000)	$ (10,000)	(12,473,000)	(57,709,000)
Repurchased common stock, shares		(1,038)
Excess tax benefit related to employee stock incentive plans	0
Balance at Dec. 31, 2017	$ 3,066,454,000	$ 937,000	$ 1,017,328,000	$ 2,048,189,000
Balance, Shares at Dec. 31, 2017		93,721

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 320,372	$ 324,596	$ 335,691
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation and amortization	102,879	89,264	64,228
Amortization of premiums, discounts and issuance costs	5,514	4,816	1,541
Stock-based compensation expense	29,573	34,000	32,129
Deferred income taxes	(60,073)	18,149	14,494
Other	(3,783)	212	(1,052)
Changes in assets and liabilities:
Accounts receivable	7,803	(34,000)	(55,391)
Prepaid expenses and other current assets	(2,792)	(783)	(4,905)
Other long-term assets	(2,709)	10,035	98
Accounts payable and accrued expenses	24,551	11,617	(7,874)
Income taxes payable	73,050	(2,234)	(4,101)
Payments of contingent consideration liabilities	(750)	(1,037)	(1,439)
Long-term professional liabilities	18,478	(3,452)	(2,064)
Other liabilities	(735)	(7,405)	(2,654)
Net cash provided from operating activities	511,378	443,778	368,701
Cash flows from investing activities:
Acquisition payments, net of cash acquired	(531,696)	(762,302)	(818,903)
Purchases of investments	(27,723)	(60,976)	(33,980)
Proceeds from maturities of investments	25,410	41,325	31,956
Purchases of property and equipment	(49,309)	(39,264)	(27,073)
Other	6,705
Net cash used in investing activities	(576,613)	(821,217)	(848,000)
Cash flows from financing activities:
Borrowings on credit agreement	2,846,000	1,940,000	2,121,500
Payments on credit agreement	(2,699,000)	(1,510,000)	(2,156,000)
Proceeds from issuance of senior notes			750,000
Payments for financing costs	(3,525)		(14,190)
Payments of contingent consideration liabilities	(5,449)	(10,740)	(12,856)
Payments on capital lease obligations	(2,267)	(2,130)	(2,171)
Excess tax benefit from exercises of stock options and vesting of restricted and deferred stock		4,241	11,583
Proceeds from issuance of common stock	23,276	22,022	20,128
Contribution from noncontrolling interests	894
Repurchases of common stock	(70,192)	(61,828)	(235,051)
Net cash provided from financing activities	89,737	381,565	482,943
Net increase in cash and cash equivalents	24,502	4,126	3,644
Cash, cash equivalents and restricted cash at beginning of year	55,698	51,572	47,928
Cash, cash equivalents and restricted cash at end of year	80,200	55,698	51,572
Supplemental disclosure of cash flow information:
Interest	73,837	60,453	20,367
Income taxes	75,427	175,962	181,005
Non-cash investing and financing activities:
Value of common stock issued for acquisitions	2,657		7,800
Equipment financed through capital leases	684	1,619	3,135
Property and equipment included in accounts payable	$ 2,700	$ 2,673	$ 1,800

General	12 Months Ended
General	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	1. General: The principal business activity of MEDNAX, Inc. (“MEDNAX” or the “Company”) and its subsidiaries is to provide neonatal, anesthesia, radiology and teleradiology, maternal-fetal and other pediatric subspecialty physician services. The Company has contracts with affiliated business corporations or professional associations, limited liability companies and partnerships (“affiliated professional contractors”), which are separate legal entities that provide physician services in certain states and Puerto Rico. The Company and its affiliated professional contractors also have contracts with hospitals and other healthcare facilities to provide physician services, which include (i) fee-for-service contracts, whereby hospitals and other customers agree, in exchange for the Company’s services, to authorize the Company and its healthcare professionals to bill and collect the charges for medical services rendered by the Company’s affiliated healthcare professionals, and (ii) administrative fee contracts, whereby the Company is assured a minimum revenue level. In addition to its national physician network, the Company also provides services nationwide to healthcare providers, including its own, through complementary businesses including a management services organization specializing in full-service revenue cycle management and a consulting services company.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary

of Significant Accounting Policies:

Principles of Presentation

The consolidated financial statements include all the accounts of the Company and its subsidiaries combined with the accounts of the affiliated professional contractors with which the Company currently has specific management arrangements. The Company’s agreements with affiliated professional contractors provide that the term of the arrangements are in most cases permanent, subject only to termination by the Company, except in the case of gross negligence, fraud or bankruptcy of the Company. The Company has the right to receive income, both as ongoing fees and as proceeds from the sale of its interest in the Company’s affiliated professional contractors, in an amount that fluctuates based on the performance of the affiliated professional contractors and the change in the fair value of the Company’s interest in the affiliated professional contractors. The Company has exclusive responsibility for the provision of all non-medical services required for the day-to-day operation and management of the Company’s affiliated professional contractors and establishes the guidelines for the employment and compensation of the physicians. In addition, the agreements provide that the Company has the right, but not the obligation, to purchase, or to designate a person(s) to purchase, the stock of the Company’s affiliated professional contractors for a nominal amount. Separately, in its sole discretion, the Company has the right to assign its interest in the agreements. Based upon the provisions of these agreements, the Company has determined that the affiliated professional contractors are variable interest entities and that the Company is the primary beneficiary as defined in the accounting guidance for consolidation. All significant intercompany and interaffiliate accounts and transactions have been eliminated.

The Company is a partner in a joint venture in which it owns a 37.5% economic interest. The Company accounts for this joint venture under the equity method of accounting because the Company exercises significant influence over, but does not control, this entity. On March 31, 2017, the Company sold its 75% economic interest in a second joint venture. The Company had a management agreement with the joint venture and, based on the terms of the agreement, the Company had determined that the joint venture was a variable interest entity for which the Company was the primary beneficiary. Accordingly, through the date of the sale, the financial results of the joint venture were fully consolidated into the Company’s operating results and the equity interests of the outside investor in the equity and results of operations of this consolidated entity were accounted for and presented as noncontrolling interests. See Note 6 for more information regarding the deconsolidation of this joint venture.

Recently Adopted Accounting Pronouncements

In January 2017, the accounting guidance related to goodwill impairment was amended to remove step two of the impairment test that requires a hypothetical purchase price allocation in order to measure the amount of any impairment. Under the new guidance, only a single-step quantitative test is required and any goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value. The new guidance does not amend the optional alternative to perform a qualitative assessment to determine if a quantitative goodwill impairment test is necessary. The Company early adopted this accounting guidance on December 31, 2017 as permitted. The adoption of this guidance did not have an impact on the Company’s Consolidated Financial Statements.

In January 2017, the accounting guidance related to business combinations was amended to clarify the definition of a business. The Company early adopted this accounting guidance on December 31, 2017 as permitted. The adoption of this guidance did not have an impact on the Company’s Consolidated Financial Statements.

In August 2016 and November 2016, the accounting guidance related to the statement of cash flows was amended with the intent of reducing diversity in practice as to the classification of certain transactions in the statement of cash flows. The Company early adopted this accounting guidance on December 31, 2017 as permitted. The adoption of this guidance resulted in the inclusion of restricted cash balances in the Company’s Consolidated Statements of Cash Flows.

In March 2016, the accounting guidance related to various aspects of share-based payment transactions was amended, including income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. Under the new guidance, excess tax benefits and deficiencies are to be recognized as income tax benefits or expenses in the income statement as discrete items in the reporting period in which they occur instead of increases or decreases to shareholders’ equity. Excess tax benefits should be classified along with other income tax cash flows as operating activities. With regard to forfeitures, the entity may make an entity-wide accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. This guidance became effective for the Company on January 1, 2017. The Company adopted this guidance prospectively for both the income statement and statement of cash flows, and the adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. The Company continues to estimate forfeitures based on the number of awards that are expected to vest.

New Accounting Pronouncements

In February 2016, the accounting guidance related to leases was issued that will require an entity to recognize leased assets and the rights and obligations created by those leased assets on the balance sheet and to disclose key information about the entity’s leasing arrangements. This guidance will become effective for the Company on January 1, 2019, with early adoption permitted. The Company expects that the adoption of this guidance will have a material impact on its Consolidated Balance Sheets and related disclosures, resulting from the recognition of significant right of use assets and related liabilities primarily related to its operating lease arrangements for space in hospitals and certain other facilities for its business and medical offices. The Company is in the process of reviewing its existing lease portfolio and accumulating all of the necessary information required to properly account for leases under the new guidance. Additionally, the Company is assessing system requirements, required changes to its processes and internal control implications to ensure the Company will meet the reporting and disclosure requirements. The Company’s evaluation of this guidance and its impacts are expected to continue through the third quarter of 2018.

In May 2014, the accounting guidance related to revenue recognition was amended to outline a single, comprehensive model for accounting for revenue from contracts with customers. The core principle of the new accounting guidance is to require an entity to recognize as revenue the amount that reflects the consideration to which it expects to be entitled in exchange for goods or services as it transfers control to its customers. The new guidance will become effective for the Company on January 1, 2018. The Company’s current revenue recognition policies for its significant revenue streams materially comply with the amended guidance. The primary change for healthcare providers under the new guidance is the requirement to report the allowance for uncollectibles associated with patient responsibility amounts as a reduction in net revenue as opposed to bad debt expense as a component of operating expenses. The Company has historically included the allowance for uncollectibles associated with patient responsibility amounts with its allowance for contractual adjustments as a reduction in net revenue as such amounts are not material. Accordingly, the adoption of this guidance will not have an impact on our Consolidated Financial Statements.

Accounting Estimates and Assumptions

The preparation of financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions are involved in the calculation of the Company’s allowance for contractual adjustments and uncollectibles on accounts receivable, liabilities for self- insured amounts and claims incurred but not reported related to the Company’s professional liability risks and the fair value of goodwill. Actual results could differ from those estimates.

Segment Reporting

The results of the Company’s operations are aggregated into a single reportable segment for purposes of presenting financial information in accordance with the accounting guidance for segment reporting.

The following table summarizes the Company’s net revenue by service line (in percentages):


	Years Ended December 31,
	2017			2016			2015
Anesthesiology		38	%		39	%		37	%
Neonatology and other pediatric subspecialties		37	%		39	%		44	%
Maternal-fetal medicine		8	%		8	%		9	%
Radiology and teleradiology		8	%		6	%		4	%
Management services		6	%		5	%		2	%
Pediatric cardiology		3	%		3	%		4	%

		100	%		100	%		100	%

Revenue Recognition

Patient service revenue is recognized at the time services are provided by the Company’s affiliated physicians. Almost all of the Company’s patient service revenue is reimbursed by government-sponsored healthcare programs and third-party insurance payors. Payments for services rendered to the Company’s patients are generally less than billed charges. The Company monitors its revenue and receivables from these sources and records an estimated contractual allowance to properly account for the anticipated differences between billed and reimbursed amounts.

Accordingly, patient service revenue is presented net of an estimated provision for contractual adjustments and uncollectibles. The Company estimates allowances for contractual adjustments and uncollectibles on accounts receivable based upon historical experience and other factors, including days sales outstanding (“DSO”) for accounts receivable, evaluation of expected adjustments and delinquency rates, past adjustments and collection experience in relation to amounts billed, an aging of accounts receivable, current contract and reimbursement terms, changes in payor mix and other relevant information. Contractual adjustments result from the difference between the physician rates for services performed and the reimbursements by government-sponsored healthcare programs and insurance companies for such services.

In addition, the Company generates revenue for services rendered under various coding and billing contracts. Contract terms are specific to each customer and may include a combination of a flat fee for coding of medical charts, a fixed fee per patient visit as well as a percentage of cash collections received by the providers. Revenue for flat and fixed fee arrangements is recognized in the month the coding occurs or the patient visit occurs. Revenue for percentage fees are recognized in the month that cash is collected for customers from payors. Revenue recorded for these services during 2017 were immaterial.

Accounts receivable are primarily amounts due under fee-for-service contracts from third-party payors, such as insurance companies, self-insured employers and patients and government-sponsored healthcare programs geographically dispersed throughout the United States and its territories. Concentration of credit risk relating to accounts receivable is limited by the number, diversity and geographic dispersion of the business units managed by the Company, as well as by the large number of patients and payors, including the various governmental agencies in the states in which the Company provides services. Receivables from government agencies made up approximately 17% of net accounts receivable at December 31, 2017 and 2016.

Cash and Cash Equivalents

Cash equivalents are defined as all highly liquid financial instruments with maturities of 90 days or less from the date of purchase. The Company’s cash equivalents typically consist of demand deposits, amounts on deposit in money market accounts, and funds invested in overnight repurchase agreements. Cash equivalent balances may, at certain times, exceed federally insured limits.

Certain cash equivalents carried by the Company are subject to the fair value provisions of the accounting guidance for fair value measurements. See “Fair Value Measurements” below.

Restricted Cash

Restricted cash consists of funds in escrow related to a potential future payment for contingent consideration for an acquisition completed during the year ended December 31, 2017. See Note 6 for more information regarding the underlying contingent consideration arrangement.

Investments

Investments consist of municipal debt securities, federal home loan securities and certificates of deposit. Investments with remaining maturities of less than one year are classified as short-term investments. Investments classified as long-term have maturities of one year to six years.

The Company intends and has the ability to hold its securities to maturity, and therefore carries such investments at amortized cost in accordance with the provisions of the accounting guidance for investments in debt securities.

Property and Equipment

Property and equipment are recorded at original purchase cost. Depreciation of property and equipment is computed using the straight-line method over the estimated useful lives of the underlying assets. Estimated useful lives are generally 30 years for buildings; three to seven years for medical equipment, computer equipment, software and furniture; and the lesser of the useful life or the remaining lease term for leasehold improvements and capital leases. Upon sale or retirement of property and equipment, the related cost and accumulated depreciation are eliminated from the respective accounts and any resulting gain or loss is included in earnings.

Business Acquisitions

The Company accounts for all business acquisitions at fair value and expenses acquisition costs as they are incurred. Any identifiable assets acquired and liabilities assumed are recognized and measured at their respective fair values on the acquisition date. If information about facts and circumstances existing as of the acquisition date is incomplete at the end of the reporting period in which a business acquisition occurs, the Company will report provisional amounts for the items for which the accounting is incomplete. The measurement period ends once the Company receives sufficient information to finalize the fair values; however, the period will not exceed one year from the acquisition date. Prior to January 1, 2016, any material adjustments recognized during the measurement period were required to be reflected retrospectively in the Consolidated Financial Statements of the subsequent period. Beginning on January 1, 2016, any adjustments to provisional amounts that are identified during the measurement period are required to be recognized in the reporting period in which the adjustment amounts are determined.

In connection with certain acquisitions, the Company enters into agreements to pay additional amounts in cash or common stock based on the achievement of certain performance measures for up to five years ending after the acquisition dates. The Company measures this contingent consideration at fair value at the acquisition date and records such contingent consideration as a liability or equity on the Company’s Consolidated Balance Sheets on the acquisition date. The fair value of each contingent consideration liability is remeasured at each reporting period with any change in fair value recognized as income or expense within operations in the Company’s Consolidated Statements of Income. See Note 6 for more information on the Company’s business acquisitions.

Goodwill and Other Intangible Assets

The Company records acquired assets and assumed liabilities at their respective fair values under the acquisition method of accounting. Goodwill represents the excess of purchase price over the fair value of the net assets acquired. Intangible assets with finite lives, principally physician and hospital agreements, customer relationships, patented technology and trade names, are recognized apart from goodwill at the time of acquisition based on the contractual-legal and separability criteria established in the accounting guidance. Intangible assets with finite lives are amortized on either an accelerated basis based on the annual undiscounted economic cash flows associated with the particular intangible asset or on a straight-line basis over their estimated useful lives. Intangible assets with finite lives are amortized over periods of one to 20 years.

Goodwill is tested for impairment at a reporting unit level on at least an annual basis in accordance with the subsequent measurement provisions of the accounting guidance for goodwill. The Company defines a reporting unit based upon its management structure for services provided in specific regions of the United States. The Company early adopted new accounting guidance in 2017 that requires only a single-step quantitative test with any goodwill impairment measured as the amount by which a reporting unit’s carrying value exceeds its fair value. The Company uses income and market-based valuation approaches to determine the fair value of its reporting units. These approaches focus on discounted cash flows and market multiples based on the Company’s market capitalization to derive the fair value of a reporting unit. The Company also considers the economic outlook for the healthcare services industry and various other factors during the testing process, including hospital and physician contract changes, local market developments, changes in third-party payor payments, and other publicly available information. The Company completed annual impairment tests in the third quarter of each of 2017, 2016 and 2015 and determined that goodwill was not impaired in any of the three years.

Long-Lived Assets

The Company is required to evaluate long-lived assets, including intangible assets subject to amortization, whenever events or changes in circumstances indicate that the carrying value of the assets may not be fully recoverable. The recoverability of such assets is measured by a comparison of the carrying value of the assets to the future undiscounted cash flows before interest charges to be generated by the assets. If long-lived assets are impaired, the impairment to be recognized is measured as the excess of the carrying value over the fair value. Long-lived assets held for disposal are reported at the lower of the carrying value or fair value less disposal costs. The Company does not believe there are any indicators that would require an adjustment to such assets or their estimated periods of recovery at December 31, 2017 pursuant to current accounting standards.

Common Stock Repurchases

The Company repurchases shares of its common stock as authorized from time to time by its Board of Directors. The Company treats repurchased shares of its common stock as retired as any repurchased shares become authorized but unissued shares. The reacquisition cost of repurchased shares is recorded as a reduction in the respective components of shareholders’ equity.

Professional Liability Coverage

The Company maintains professional liability insurance policies with third-party insurers generally on a claims-made basis, subject to deductibles or self-insured retention, exclusions and other restrictions. The Company’s self-insured retention under its professional liability insurance program is maintained primarily through a wholly owned captive insurance subsidiary. The Company records an estimate of liabilities for self-insured amounts and claims incurred but not reported based on an actuarial valuation using historical loss information, claim emergence patterns and various actuarial assumptions. Liabilities for claims incurred but not reported are not discounted.

Income Taxes

The Company records deferred income taxes using the liability method, whereby deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. If it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is provided against such deferred tax assets. In making such determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations.

The accounting guidance for uncertain tax positions prescribes a recognition threshold and measurement attribute for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The guidance also requires policy disclosures regarding penalties and interest and extensive disclosures regarding increases and decreases in uncertain tax positions as a result of tax positions taken in a current or prior period, settlements with taxing authorities and any lapse of an applicable statute of limitations. Additional qualitative discussion is required for any tax position that may result in a significant increase or decrease in uncertain tax positions within a 12-month period from the Company’s reporting date.

Stock Incentive Plans

The Company grants stock-based awards consisting primarily of restricted stock to key employees under its Amended and Restated 2008 Incentive Compensation Plan, as amended. The Company measures the cost of employee services received in exchange for stock-based awards based on grant-date fair value and allocates the resulting compensation expense over the corresponding requisite service period using the graded vesting attribution method. The Company also performs analyses to estimate forfeitures of stock-based awards on an annual basis and adjusts the estimates as necessary based on the number of awards that ultimately vest.

Net Income Per Common Share

Basic net income per common share is calculated by dividing net income by the weighted average number of common shares outstanding during the period. Diluted net income per common share is calculated by dividing net income by the weighted average number of common and potential common shares outstanding during the period. Potential common shares consist of outstanding restricted stock, deferred stock and stock options and is calculated using the treasury stock method. On January 1, 2017, the Company adopted new accounting guidance that no longer permits the Company to include the assumed excess tax benefits related to the potential exercise or vesting of its stock-based awards in the treasury stock method computation. The impact on the weighted average number of common and common equivalent shares outstanding from excluding such assumed excess tax benefits for the year ended December 31, 2017 was not material. See “Recently Adopted Accounting Pronouncements” above for additional information on the adoption of the new accounting guidance.

Fair Value Measurements

In accordance with the accounting guidance for fair value measurements and disclosures, the Company carries its money market funds included in cash and cash equivalents at fair value. In accordance with the three-tier fair value hierarchy under this guidance, the Company determined the fair value using quoted market prices, a Level 1 input as defined under the accounting guidance for fair value measurements. At December 31, 2017 and 2016, the Company’s money market funds had a fair value of $9.2 million and $12.4 million, respectively.

The Company also carries the cash surrender value of life insurance related to its deferred compensation arrangements at fair value. The investments underlying the life insurance contracts consist primarily of exchange-traded equity securities and mutual funds with quoted prices in active markets. In accordance with the three-tier fair value hierarchy, the Company determined the fair value using the cash surrender value of the life insurance, a Level 2 input as defined under the accounting guidance for fair value measurements. At December 31, 2017 and 2016, the Company’s cash surrender value of life insurance had a fair value of $15.6 million and $15.8 million, respectively.

In addition, the Company carries its contingent consideration liabilities related to acquisitions at fair value. In accordance with the three-tier fair value hierarchy, the Company determined the fair value of its contingent consideration liabilities using the income approach with assumed discount rates and payment probabilities. The income approach uses Level 3, or unobservable inputs as defined under the accounting guidance for fair value measurements. At December 31, 2017 and 2016, the Company’s contingent consideration liabilities had a fair value of $30.5 million and $17.3 million, respectively. See Note 6 for more information regarding the Company’s contingent consideration liabilities.

The carrying amounts of cash equivalents, short-term investments, accounts receivable and accounts payable and accrued expenses approximate fair value due to the short maturities of the respective instruments. The carrying values of long-term investments, line of credit, variable rate long-term debt and capital lease obligations approximate fair value. If the Company’s investments were measured at fair value, they would be categorized as Level 2 in the fair value hierarchy. If the Company’s line of credit and variable long-term debt were measured at fair value, they would be categorized as Level 2 in the fair value hierarchy. See Note 10 for information regarding the fair value of the Company’s 5.25% senior unsecured notes due 2023 (the “2023 Notes”).

Investments

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Investments

3. Investments:

Investments held are summarized as follows (in thousands):


	December 31, 2017				December 31, 2016
	Short-Term		Long-Term		Short-Term		Long-Term
Municipal debt securities	$	8,312	$	46,195	$	10,306	$	46,513
Federal home loan securities		1,000		30,322		—		28,747
Certificates of deposit		980		4,165		980		3,715

	$	10,292	$	80,682	$	11,286	$	78,975

Contractual maturities of long-term investments are summarized as follows (in thousands):


	December 31,
	2017		2016
Due after one year through five years	$	78,561	$	70,005
Due after five years through six years		2,121		8,970

	$	80,682	$	78,975

Accounts Receivable and Net Revenue

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Accounts Receivable and Net Revenue

4. Accounts Receivable and Net Revenue:

Accounts receivable, net consists of the following (in thousands):


	December 31,
	2017			2016
Gross accounts receivable	$	1,790,034		$	1,719,642
Allowance for contractual adjustments and uncollectibles		(1,286,035	)		(1,224,366	)

	$	503,999		$	495,276

Net revenue consists of the following (in thousands):


	Years Ended December 31,
	2017			2016			2015
Gross revenue	$	11,427,238		$	10,374,813		$	8,942,957
Contractual adjustments and uncollectibles		(8,285,317	)		(7,464,030	)		(6,389,195	)
Hospital contract administrative fees		316,391			272,376			226,234

	$	3,458,312		$	3,183,159		$	2,779,996

Accounts receivable of $504.0 million and $495.3 million at December 31, 2017 and 2016, respectively, consist primarily of amounts due from government-sponsored healthcare programs and third-party insurance payors for services provided by the Company’s affiliated physicians.

Net revenue of $3.5 billion, $3.2 billion and $2.8 billion for the years ended December 31, 2017, 2016 and 2015, respectively, consists primarily of gross billed charges for services provided by the Company’s affiliated physicians less an estimated allowance for contractual adjustments and uncollectibles to properly account for the anticipated differences between gross billed charge amounts and expected reimbursement amounts.

The Company’s contractual adjustments and uncollectibles as a percentage of gross patient service revenue vary slightly each year depending on several factors, including improved managed care contracting, changes in reimbursement from state Medicaid programs and other government-sponsored programs, shifts in the percentage of patient services being reimbursed under government-sponsored programs and annual price increases.

The Company’s annual price increases typically increase contractual adjustments as a percentage of gross patient service revenue. This increase is primarily due to Medicaid, Medicare and other government-sponsored healthcare programs that generally provide for reimbursements on a fee-schedule basis rather than on a gross charge basis. When the Company bills these programs, like other payors, on a gross-charge basis, it also increases its provision for contractual adjustments and uncollectibles by the amount of any price increase, resulting in a higher contractual adjustment percentage.

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment

5. Property and Equipment:

Property and equipment consists of the following (in thousands):


	December 31,
	2017			2016
Building	$	33,024		$	26,572
Land		6,683			6,683
Equipment and other		253,453			213,521

		293,160			246,776
Accumulated depreciation		(169,624	)		(143,708	)

	$	123,536		$	103,068

At December 31, 2017 and 2016, property and equipment includes medical and other equipment held under capital leases of $6.1 million and $6.2 million, and related accumulated depreciation of $4.6 million and $4.0 million, respectively. The Company recorded depreciation expense of $33.9 million, $29.0 million and $22.2 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Business Acquisitions

12 Months Ended

Dec. 31, 2017

Business Combinations [Abstract]

Business Acquisitions

6. Business Acquisitions:

During the year ended December 31, 2017, the Company completed 10 physician group practice acquisitions, including four radiology practices, two maternal-fetal medicine practices, one neonatology practice, one pediatric multi-specialty practice and two other pediatric subspecialty practices. The acquisition-date fair value of the total consideration for the 10 acquisitions was $554.0 million, net of cash acquired. Approximately $531.7 million was paid in cash, $2.7 million was paid by issuing 69,014 shares of the Company’s common stock, $18.6 million was recorded as a contingent consideration liability and $1.0 million was recorded as accrued purchase consideration within other current liabilities.

These acquisitions expanded the Company’s national network of physician practices. The Company expects to improve the results of physician practices through improved managed care contracting, improved collections and identification of growth initiatives, as well as operating and cost savings based on the significant infrastructure it has developed. With respect to the Company’s acquisition of radiology physician practices, the Company believes that it brings a unique value proposition to radiology physician groups, in that the Company can provide not only practice support, but also teleradiology capabilities that can enhance a physician group’s efficiency, provide subspecialty access and help them grow, remain competitive and meet the ever increasing demands of their hospital partners, payors and regulatory bodies. In addition, the Company believes that radiology physician group practice physicians can complement the staffing needs for its teleradiology services business during certain times, such as nights and weekends, when such physicians are not providing services at their practices.

The 69,014 shares of the Company’s common stock issued as a component of the purchase consideration for acquisitions completed during the first quarter and fourth quarter of 2017 had an acquisition-date fair value of $2.7 million. The fair value of such shares was determined using the closing price on the New York Stock Exchange of the Company’s common stock less a discount for lack of marketability on the respective dates of acquisition, reflecting a three year contractual restriction on the disposition or assignment of such common stock.

The Company’s preliminary allocation of purchase price is as follows (in thousands):


Current assets	$	43,550
Property and equipment		5,281
Other noncurrent assets		52,611
Goodwill		439,822
Other intangible assets		39,414
Current liabilities		(5,674	)
Other long-term liabilities		(21,086	)

	$	553,918

The Company has recorded provisional amounts for deferred income taxes related to certain acquisitions completed during the year ended December 31, 2017. Any adjustments will be recorded during the measurement period and are not expected to be material.

Current assets acquired and other noncurrent assets acquired include assets with a fair value of $23.5 million and $22.5 million, respectively, that are expected to be sold and contributed to a joint venture for an equity method investment in that joint venture, respectively, within the next twelve months. Accordingly, these assets are classified as held for sale.

The contingent consideration of $18.6 million recorded during the year ended December 31, 2017 is related to an agreement to pay an additional cash amount based on the achievement of certain performance measures for the period through June 1, 2019. The accrued contingent consideration was recorded as a liability at acquisition-date fair value using the income approach with assumed discount rates ranging from 4.0% to 4.75% over the applicable terms and an assumed payment probability assessment over the applicable years. The range of the undiscounted amount the Company could pay under the contingent consideration agreement is between $0 and $20.0 million. In connection with this contingent consideration arrangement, the Company has designated $20.0 million as restricted cash in its Consolidated Balance Sheet. In addition, during the year ended December 31, 2017, the Company paid $6.2 million for contingent consideration related to certain prior-period acquisitions, of which all but the accretion recorded during 2017 was accrued as of December 31, 2016.

In connection with certain prior period acquisitions, the Company recorded an increase in deferred tax liabilities of $0.5 million with a corresponding increase in goodwill of $0.5 million resulting from the finalization of income tax acquisition accounting.

During the year ended December 31, 2016, the Company completed 15 acquisitions, of which 13 were physician group practices including eight anesthesiology practices, two other pediatric subspecialty practices, one neonatology practice, one maternal-fetal medicine practice and one pediatric cardiology practice. In addition, the Company acquired a third-party receivables company and a patient engagement software company as additions to its existing management services organization. The total consideration for the 15 acquisitions was $759.6 million, net of $15.0 million cash acquired, of which $756.1 million was paid in cash and $3.5 million was recorded as a contingent consideration liability.

On March 31, 2017, the Company sold its 75% economic interest in a joint venture that was previously consolidated. The deconsolidation and removal of 100% of the carrying value of the joint venture’s net assets resulted in a gain on sale that was not material.

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

7. Goodwill and Intangible Assets:

Goodwill was $4.3 billion and $3.8 billion at December 31, 2017 and 2016, respectively. The change in the carrying amount of goodwill of $438.8 million during the year ended December 31, 2017 is primarily related to the Company’s 2017 acquisitions. The Company expects that $159.5 million of the goodwill recorded during the year ended December 31, 2017 will be deductible for tax purposes.

Intangible assets, net, consist of the following (in thousands):


	December 31, 2017
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Physician and hospital agreements	$	381,635	$	(203,915	)	$	177,720
Customer relationships		443,300		(48,837	)		394,463
Trade names		43,156		(2,933	)		40,223
Patented and other technology		38,590		(11,068	)		27,522

	$	906,681	$	(266,753	)	$	639,928


	December 31, 2016
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Physician and hospital agreements	$	347,862	$	(168,488	)	$	179,374
Customer relationships		443,300		(27,368	)		415,932
Trade names		43,156		(1,604	)		41,552
Patented and other technology		37,503		(5,832	)		31,671

	$	871,821	$	(203,292	)	$	668,529

During the year ended December 31, 2017, the Company recorded intangible assets related to acquisitions totaling $39.4 million, consisting primarily of physician and hospital agreements. The weighted-average amortization period for these physician and hospital agreements is approximately 10 years.

Amortization expense for intangible assets was $68.9 million, $60.3 million and $42.0 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Amortization expense for existing intangible assets for the next five years is expected to be as follows (in thousands):


2018	$	67,514
2019		62,669
2020		56,636
2021		51,069
2022		44,357

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Accounts Payable and Accrued Expenses

8. Accounts Payable and Accrued Expenses:

Accounts payable and accrued expenses consist of the following (in thousands):


	December 31,
	2017		2016
Accounts payable	$	34,632	$	28,474
Accrued salaries and bonuses		225,429		220,635
Accrued payroll taxes and benefits		75,672		67,830
Accrued professional liabilities		37,912		28,972
Accrued contingent consideration		6,259		6,566
Accrued interest		4,495		4,511
Other accrued expenses		53,618		50,950

	$	438,017	$	407,938

Accrued Professional Liabilities

12 Months Ended

Dec. 31, 2017

Health Care Organizations [Abstract]

Accrued Professional Liabilities

9. Accrued Professional Liabilities:

At December 31, 2017 and 2016, the Company’s total accrued professional liabilities of $250.2 million and $202.1 million, respectively, includes incurred but not reported loss reserves of $138.5 million and $128.1 million, respectively, and loss reserves for reported claims of $111.7 million and $74.0 million, respectively. Of the total liability, $37.9 million is classified as a current liability within accounts payable and accrued expenses in the Consolidated Balance Sheet. In addition, there is a corresponding insurance receivable of $18.9 million recorded as a component of other assets for certain professional liability claims that are covered by third-party insurance policies.

The activity related to the Company’s total accrued professional liability for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands):


	Years Ended December 31,
	2017			2016			2015
Balance at beginning of year	$	202,052		$	202,527		$	168,369
Assumed liabilities through acquisition		20,716			—			35,968
Provision (adjustment) for losses related to:
Current year		41,291			38,129			39,204
Prior years		9,983			(25,428	)		(25,797	)

Total provision for losses		51,274			12,701			13,407
Claim payments related to:
Current year		(712	)		(766	)		(1,382	)
Prior years		(23,143	)		(12,410	)		(13,835	)

Total payments		(23,855	)		(13,176	)		(15,217	)

Balance at end of year	$	250,187		$	202,052		$	202,527

The net increase in the Company’s total accrued professional liability for the year ended December 31, 2017 is primarily related to growth in the program from acquisitions as well as overall unfavorable trends in the Company’s claims experience. The net decrease in 2016 was primarily attributable to the overall favorable trends in the Company’s claims experience.

Line of Credit, Long-Term Debt and Capital Lease Obligations

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Line of Credit, Long-Term Debt and Capital Lease Obligations

10. Line of Credit, Long-Term Debt and Capital Lease Obligations:

On October 30, 2017, the Company entered into a new credit agreement (the “New Credit Agreement”), which replaces the Company’s prior credit agreement. The New Credit Agreement provides for a $2.0 billion unsecured revolving credit facility and includes a $37.5 million sub-facility for the issuance of letters of credit. The New Credit Agreement matures on October 31, 2022 and is guaranteed by substantially all of the Company’s subsidiaries and affiliated professional associations and corporations. At the Company’s option, borrowings under the New Credit Agreement will bear interest at (i) the alternate base rate (defined as the higher of (a) the prime rate, (b) the Federal Funds Rate plus 1/2 of 1.00% and (c) LIBOR for an interest period of one month plus 1.00%) plus an applicable margin rate ranging from 0.125% to 0.750% based on the Company’s consolidated leverage ratio or (ii) the LIBOR rate plus an applicable margin rate ranging from 1.125% to 1.750% based on the Company’s consolidated leverage ratio. The New Credit Agreement also calls for other customary fees and charges, including an unused commitment fee ranging from 0.150% to 0.300% of the unused lending commitments, based on the Company’s consolidated leverage ratio.

The New Credit Agreement contains customary covenants and restrictions, including covenants that require the Company to maintain a minimum interest charge ratio, not to exceed a specified consolidated leverage ratio and to comply with laws, and restrictions on the ability of the Company to pay dividends and make certain other distributions, as specified therein. Failure to comply with these covenants would constitute an event of default under the New Credit Agreement, notwithstanding the ability of the Company to meet its debt service obligations. The New Credit Agreement also includes various customary remedies for the lenders following an event of default, including the acceleration of repayment of outstanding amounts under the New Credit Agreement.

On December 8, 2015, the Company completed a private offering of $750.0 million aggregate principal amount of 2023 Senior Notes. The Company’s obligations under the 2023 Senior Notes are guaranteed on an unsecured senior basis by the same subsidiaries and affiliated professional contractors that guarantee the Credit Agreement. Interest on the 2023 Senior Notes accrues at the rate of 5.25% per annum and is payable semi-annually in arrears on June 1 and December 1.

At any time prior to December 1, 2018, the Company may redeem all or a portion of the 2023 Senior Notes at a redemption price equal to 100% of the principal amount of the notes being redeemed plus an applicable redemption premium and accrued and unpaid interest to the redemption date. In addition, at any time prior to December 1, 2018, the Company may redeem up to 35% of the aggregate principal amount of the 2023 Senior Notes at a redemption price of 105.250% of the principal amount thereof, plus accrued and unpaid interest, if any, to the redemption date, using proceeds from one or more equity offerings. On or after December 1, 2018, the Company may redeem all or a portion of the 2023 Senior Notes, at the redemption prices of 103.938% in 2018, 102.625% in 2019, 101.313% in 2020 and 100% in 2021 and thereafter, plus accrued and unpaid interest to the redemption date.

The indenture under which the 2023 Senior Notes are issued, among other things, limits our ability to (1) incur liens and (2) enter into sale and lease-back transactions, and also limits our ability to merge or dispose of all or substantially all of our assets, in all cases, subject to a number of customary exceptions. Although we are not required to make mandatory redemption or sinking fund payments with respect to the 2023 Senior Notes, upon the occurrence of a change in control of MEDNAX, we may be required to repurchase the 2023 Senior Notes at a purchase price equal to 101% of the aggregate principal amount of the 2023 Senior Notes repurchased plus accrued and unpaid interest.

The Company presents issuance costs related to long-term debt liabilities, other than revolving credit arrangements, as a direct deduction from the carrying value of that long-term debt.

The carrying value of the Company’s long-term debt was $1.8 billion and $1.7 billion at December 31, 2017 and 2016, respectively, and consisted of the following (in thousands):


	December 31, 2017
	Principal		Unamortized Debt Issuance Costs			Total
2023 Senior Notes	$	750,000	$	(9,503	)	$	740,497
Revolving line of credit		1,110,500		(4,864	)		1,105,636

Total	$	1,860,500	$	(14,367	)	$	1,846,133


	December 31, 2016
	Principal			Unamortized Debt Issuance Costs			Total
2023 Senior Notes	$	750,000		$	(11,109	)	$	738,891
Revolving line of credit		783,500			(3,388	)		780,112
Term loan		180,000			(259	)		179,741

		1,713,500			(14,756	)		1,698,744
Less: Current portion		(20,000	)		—			(20,000	)

Long-term portion	$	1,693,500		$	(14,756	)	$	1,678,744

The Company has outstanding letters of credit which reduced the amount available under the New Credit Agreement by $0.2 million at December 31, 2017. At December 31, 2017, the Company had an available balance on its New Credit Agreement of $889.3 million.

The carrying values of the Company’s variable rate revolving line of credit approximates fair value due to the short-term nature of the interest rates. The estimated fair value of the Company’s 2023 Notes was $763.1 million and $773.4 million, at December 31, 2017 and 2016, respectively, and was estimated using trading prices as of December 31, 2017 and December 31, 2016 as Level 2 inputs to estimate fair value.

The Company’s capital lease obligations consist of the following (in thousands):


	December 31,
	2017			2016
Capital lease obligations	$	1,826		$	3,550
Less: Current portion		(1,401	)		(2,054	)

Long-term portion	$	425		$	1,496

The amounts due under the terms of the Company’s capital lease obligations at December 31, 2017 are as follows:


2018	$	1,401
2019		238
2020		113
2021		74

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes:

The components of the income tax provision (benefit) are as follows (in thousands):


	December 31,
	2017			2016		2015
Federal:
Current	$	130,053		$	166,758	$	168,596
Deferred		(63,038	)		15,596		12,866

		67,015			182,354		181,462

State:
Current		20,070			4,296		20,948
Deferred		2,965			2,553		1,628

		23,035			6,849		22,576

Total	$	90,050		$	189,203	$	204,038

The Company files its tax return on a consolidated basis with its subsidiaries. The remaining affiliated professional contractors file tax returns on an individual basis.

The effective tax rate was 21.94%, 36.80% and 37.76% for the years ended December 31, 2017, 2016 and 2015, respectively. During the three months ended December 31, 2017, the Company recorded a $70.0 million income tax benefit related to the reduction of its net deferred tax liability resulting from the reduction in the corporate tax rate enacted in December 2017 under the Tax Cuts and Jobs Act of 2017. Excluding this favorable impact, our effective income tax rate for the year ended December 31, 2017 was 39.00%. During the three months ended September 30, 2016, the Company settled a certain tax matter with a taxing authority. In connection with this settlement, the Company’s effective income tax rate was favorably impacted by $10.6 million. Excluding this favorable impact, the effective tax rate for December 31, 2016 was 38.87%, as compared to 37.76% for 2015.

The differences between the effective rate and the United States federal income tax statutory rate are as follows:


	December 31,
	2017			2016			2015
Tax at statutory rate		35.00	%		35.00	%		35.00	%
State income tax, net of federal benefit		3.33			2.94			2.97
Non-deductible expenses		0.49			0.43			0.34
Change in accrual estimates relating to uncertain tax positions		0.02			(2.11	)		(0.43	)
Change in valuation allowance		—			0.48			0.29
Other, net		0.16			0.06			(0.41	)
Change in tax law		(17.06	)		—			—

Income tax provision		21.94	%		36.80	%		37.76	%

All of the Company’s deferred tax assets and liabilities are classified as long-term. The significant components of deferred income tax assets and liabilities are as follows (in thousands):


	December 31,
	2017			2016
Allowance for uncollectible accounts	$	80,056		$	103,525
Reserves and accruals		45,454			62,212
Stock-based compensation		7,975			13,726
Net operating loss carryforward		28,569			49,156
Property and equipment		685			1,621
Other		970			1,610

Deferred tax assets before valuation allowance		163,709			231,850
Less: Valuation allowance		(2,615	)		(4,014	)

Deferred tax assets, net of valuation allowance		161,094			227,836

Gross deferred tax liabilities:
Amortization		(258,618	)		(380,594	)
Accrual to cash adjustment		(31,290	)		(53,771	)
Other		(4,150	)		(1,023	)

Total deferred tax liabilities		(294,058	)		(435,388	)

Net deferred tax liability	$	(132,964	)	$	(207,552	)

The Company’s net deferred tax liability decreased by $74.6 million during 2017 of which $70.0 million is related to a reduction in the corporate tax rate enacted under the Tax Cuts and Jobs Act of 2017.

Beginning January 1, 2017, excess tax benefits or deficiencies associated with the exercise of stock options, the vesting of restricted and deferred stock and the purchase of shares under the Company’s non-qualified employee stock purchase plan are recognized as income tax benefits or expenses in the income statement in the reporting period in which they occur instead of an increase or decrease to additional paid-in-capital. For the year ended December 31, 2017, income tax expense of $0.2 million was recognized for excess tax deficiencies. For the years ended December 31, 2016 and 2015, respectively, additional paid-in-capital was increased by $4.2 million and $11.6 million for excess tax benefits.

The Company has net operating loss carryforwards for federal and state tax purposes totaling $116.0 million, $130.0 million, and $136.6 million at December 31, 2017, 2016 and 2015, respectively, expiring at various times in 2019 through 2037.

As of December 31, 2017, 2016 and 2015, the Company’s liability for uncertain tax positions, excluding accrued interest and penalties, was $11.0 million, $9.5 million and $18.4 million, respectively. As of December 31, 2017, the Company had $10.7 million of uncertain tax positions that, if recognized, would favorably impact its effective tax rate.

The following table summarizes the activity related to the Company’s liability for uncertain tax positions for the years ended December 31, 2017, 2016 and 2015 (in thousands):


	Years Ended December 31,
	2017			2016			2015
Balance at beginning of year	$	9,469		$	18,447		$	17,165
Increases related to prior year tax positions		2,284			301			467
Decreases related to prior year tax positions		(143	)		(3,927	)		(1,168	)
Increases related to current year tax positions		1,430			2,258			3,675
Settlements		—			(5,644	)		—
Decreases related to lapse of statutes of limitation		(2,068	)		(1,966	)		(1,692	)

Balance at end of year	$	10,972		$	9,469		$	18,447

During the year ended December 31, 2017, the Company increased its liability for uncertain tax positions by a total of $1.5 million, primarily related to additional taxes on current and prior year positions, partially offset by the expiration of statutes of limitation. During the year ended December 31, 2016, the Company decreased its liability for uncertain tax positions by a total of $9.0 million, primarily related to the settlement of a certain tax matter with a taxing authority and the expiration of statutes of limitation, partially offset by additional taxes on current year positions.

In addition, the Company anticipates that its liability for uncertain tax positions will be decreased by $1.1 million related to the expiration of certain statutes of limitation over the next 12 months.

The Company includes interest and penalties related to income tax liabilities in income tax expense. The Company recognized an income tax benefit of $0.2 million and $7.9 million and income tax expense of $0.6 million related to interest and penalties during the years ended December 31, 2017, 2016 and 2015, respectively. At December 31, 2017 and 2016, the Company’s accrued liability for interest and penalties related to income tax liabilities totaled $1.2 million and $1.4 million, respectively.

The Company is currently subject to U.S. Federal and various state income tax examinations for the tax years 2013 through 2016.

Common and Common Equivalent Shares

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Common and Common Equivalent Shares

12. Common and Common Equivalent Shares:

The calculation of shares used in the basic and diluted net income per share calculation for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands):


	Years Ended December 31,
	2017		2016		2015
Weighted average number of common shares outstanding		92,431		92,422		93,077
Weighted average number of dilutive common share equivalents		527		687		883

Weighted average number of common and common equivalent shares outstanding		92,958		93,109		93,960

Antidilutive securities not included in the diluted net income per common share calculation		107		2		—

Stock Incentive Plans and Stock Purchase Plans

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Incentive Plans and Stock Purchase Plans

13. Stock Incentive Plans and Stock Purchase Plans:

The Company’s Amended and Restated 2008 Incentive Compensation Plan, as amended (the “Amended and Restated 2008 Incentive Plan”) provides for grants of stock options, stock appreciation rights, restricted stock, deferred stock, and other stock-related awards and performance awards that may be settled in cash, stock or other property.

Under the Amended and Restated 2008 Incentive Plan, options to purchase shares of common stock may be granted at a price not less than the fair market value of the shares on the date of grant. The options must be exercised within 10 years from the date of grant and generally become exercisable on a pro rata basis over a three-year period from the date of grant. The Company issues new shares of its common stock upon exercise of its stock options. Restricted stock awards generally vest over periods of three years upon the fulfillment of specified service-based conditions and in certain instances performance-based conditions. Deferred stock awards generally vest upon the satisfaction of specified performance-based conditions or service-based conditions. The Company recognizes compensation expense related to its restricted stock and deferred stock awards ratably over the corresponding vesting periods. At December 31, 2017, the Company had 3.4 million shares available for future grants and awards under its Amended and Restated 2008 Incentive Plan.

Under the Company’s 1996 Non-Qualified Employee Stock Purchase Plan, as amended (the “ESPP”), employees are permitted to purchase the Company’s common stock at 85% of market value on January 1st, April 1st, July 1st and October 1st of each year. Under the Company’s 2015 Non-Qualified Stock Purchase Plan (the “SPP”), certain eligible non-employee service providers are permitted to purchase the Company’s common stock at 90% of market value on January 1st, April 1st, July 1st and October 1st of each year upon the SPP’s effective date of January 1, 2016.

Each of the ESPP and the SPP provide for the issuance of an of aggregate 2.6 million shares of the Company’s common stock less the number of shares of common stock purchased under the other plan. The Company recognizes stock-based compensation expense for the discount received by participating employees and non-employee service providers. During the year ended December 31, 2017, 0.4 million shares were issued under the ESPP and SPP. At December 31, 2017, the Company had 1.9 million shares in aggregate reserved for issuance under the ESPP and SPP.

The Company recognized $29.6 million, $34.0 million and $32.1 million of stock-based compensation expense related to its stock incentive plans, the ESPP and the SPP during the years ended December 31, 2017, 2016 and 2015, respectively.

The activity related to the Company’s restricted stock and deferred stock awards and the corresponding weighted average grant-date fair values for the year ended December 31, 2017 are as follows:


	Number of Shares			Weighted Average Fair Value
Non-vested shares at January 1, 2017		946,329		$	66.98
Awarded		637,529		$	54.22
Forfeited		(91,730	)	$	64.82
Vested		(451,094	)	$	65.00

Non-vested shares at December 31, 2017		1,041,034		$	60.21

The aggregate fair value of the restricted and deferred stock that vested during the years ended December 31, 2017, 2016 and 2015 was $29.3 million, $29.8 million and $31.6 million, respectively.

The weighted average grant-date fair value of restricted and deferred stock awards that were granted during the years ended December 31, 2017, 2016 and 2015 was $54.22, $67.90 and $70.44, respectively.

At December 31, 2017, the total stock-based compensation cost related to non-vested restricted and deferred stock remaining to be recognized as compensation expense over a weighted-average period of 1.6 years was $30.9 million.

The Company did not grant any stock options in 2017, 2016 or 2015, and all stock-based compensation cost related to stock options has been recognized. The activity and certain other information related to the Company’s outstanding stock option awards for the year ended December 31, 2017 are as follows:


	Number of Stock Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at January 1, 2017		410,286		$	28.33
Exercised		(163,944	)	$	29.57			$	5.5

Outstanding and exercisable at December 31, 2017		246,342		$	27.51		1.5	$	6.4

The aggregate intrinsic value of stock options exercised during the years ended December 31, 2017, 2016 and 2015 was $5.5 million, $6.8 million and $11.3 million, respectively.

There were no excess tax benefits recognized in additional paid-in capital due to the adoption of new accounting guidance on January 1, 2017 that requires excess tax benefits to be recognized in the income statement. The net excess tax benefit recognized in additional paid-in capital related primarily to stock options, restricted stock and deferred stock for the years ended December 31, 2016 and 2015 was $4.1 million and $11.6 million, respectively. The cash proceeds received from the exercise of stock options for the years ended December 31, 2017, 2016 and 2015 were $4.8 million, $4.7 million and $6.1 million, respectively.

Common Stock Repurchase Programs	12 Months Ended
Common Stock Repurchase Programs	Dec. 31, 2017
Text Block [Abstract]
Common Stock Repurchase Programs	14. Common Stock Repurchase Programs: In July 2013, the Company’s Board of Directors authorized the repurchase of shares of the Company’s common stock up to an amount sufficient to offset the dilutive impact from the issuance of shares under the Company’s equity compensation programs. The share repurchase program allows the Company to make open market purchases from time-to-time based on general economic and market conditions and trading restrictions. The repurchase program also allows for the repurchase of shares of the Company’s common stock to offset the dilutive impact from the issuance of shares, if any, related to the Company’s acquisition program. During the year ended December 31, 2017, the Company repurchased 1.0 million shares of its common stock for $70.2 million, inclusive of 38,257 shares withheld to satisfy minimum statutory withholding obligations of $2.1 million in connection with the vesting of restricted stock. In October 2014, the Company’s Board of Directors authorized the repurchase of up to $600.0 million of shares of the Company’s common stock in addition to its existing share repurchase program. In December 2014, the Company entered into an uncollared accelerated share repurchase (“ASR”) agreement with an investment bank. Under the ASR agreement, the Company agreed to purchase $200.0 million of its common stock in total. On December 17, 2014, the Company paid a total of $200.0 million to an investment bank, which in turn delivered to the Company 2.5 million shares of the Company’s common stock in total based on the market price of a share of Company common stock on December 12, 2014. The payment was recorded as a reduction to the respective components of shareholders’ equity. The final number of shares of common stock that the Company may receive, or may be required to remit, upon settlement under the ASR agreement was to be based upon the average daily volume weighted-average price of the Company’s common stock during the term of the ASR agreement, less a negotiated discount. The ASR agreement was funded by borrowings under the Company’s Credit Agreement discussed in Note 10. Final settlement of the ASR occurred in July 2015 with the delivery to the Company of 0.3 million additional shares of common stock. The final number of shares of common stock that the Company received was based upon the average daily volume weighted-average price of the Company’s common stock during the term of the ASR agreement, less a negotiated discount. In March 2015, the Company entered into a second uncollared ASR agreement with an investment bank. Under the ASR agreement, the Company agreed to purchase $200.0 million of its common stock in total. On March 16, 2015, the Company paid a total of $200.0 million to an investment bank, which in turn delivered to the Company 2.2 million shares of the Company’s common stock in total based on the market price of a share of Company common stock on March 12, 2015. The ASR agreement was funded by borrowings under the Company’s Credit Agreement, and the payment was recorded as a reduction to the respective components of shareholders’ equity. Final settlement of the ASR occurred in October 2015 with the delivery to the Company of 0.3 million additional shares of common stock. The final number of shares of common stock that the Company received was based upon the average daily volume weighted-average price of the Company’s common stock during the term of the ASR agreement, less a negotiated discount. During the year ended December 31, 2016, the Company repurchased 0.9 million shares of its common stock for $61.8 million, inclusive of 46,490 shares withheld to satisfy minimum stock withholding obligations of $3.2 million in connection with the vesting of restricted stock. The Company intends to utilize various methods to effect any future share repurchases, including, among others, open market purchases and accelerated share repurchase programs. The amount and timing of repurchases will depend upon several factors, including general economic and market conditions and trading restrictions.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

16. Commitments and Contingencies:

The Company expects that audits, inquiries and investigations from government authorities and agencies will occur in the ordinary course of business. Such audits, inquiries and investigations and their ultimate resolutions, individually or in the aggregate, could have a material adverse effect on the Company’s business, financial condition, results of operations, cash flows and the trading price of its common stock. The Company has not included an accrual for these matters as of December 31, 2017 in its Consolidated Financial Statements, as the variables affecting any potential eventual liability depend on the currently unknown facts and circumstances that arise out of, and are specific to, any particular future audit, inquiry and investigation and cannot be reasonably estimated at this time.

In the ordinary course of business, the Company becomes involved in pending and threatened legal actions and proceedings, most of which involve claims of medical malpractice related to medical services provided by the Company’s affiliated physicians. The Company’s contracts with hospitals generally require the Company to indemnify them and their affiliates for losses resulting from the negligence of the Company’s affiliated physicians. The Company may also become subject to other lawsuits which could involve large claims and significant costs. The Company believes, based upon a review of pending actions and proceedings, that the outcome of such legal actions and proceedings will not have a material adverse effect on its business, financial condition, results of operations, cash flows and the trading price of its securities. The outcome of such actions and proceedings, however, cannot be predicted with certainty and an unfavorable resolution of one or more of them could have a material adverse effect on the Company’s business, financial condition, results of operations, cash flows and the trading price of its securities.

Although the Company currently maintains liability insurance coverage intended to cover professional liability and certain other claims, the Company cannot assure that its insurance coverage will be adequate to cover liabilities arising out of claims asserted against it in the future where the outcomes of such claims are unfavorable. With respect to professional liability risk, the Company generally self-insures a portion of this risk through its wholly owned captive insurance subsidiary. Liabilities in excess of the Company’s insurance coverage, including coverage for professional liability and certain other claims, could have a material adverse effect on the Company’s business, financial condition, results of operations, cash flows and the trading price of its securities.

The Company leases space for its regional, medical and business offices, storage space and temporary housing of medical staff. The Company also leases an aircraft. Rent expense for the years ended December 31, 2017, 2016 and 2015 was $42.6 million, $38.0 million and $31.6 million, respectively.

Future minimum lease payments under non-cancelable operating leases as of December 31, 2017 are as follows (in thousands):


2018	$	34,337
2019		24,178
2020		16,633
2021		12,065
2022		8,125
Thereafter		9,934

	$	105,272

Selected Quarterly Financial Information

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Information

17. Selected Quarterly Financial Information (Unaudited):

The following tables set forth a summary of the Company’s selected quarterly financial information for each of the four quarters ended December 31, 2017 and 2016 (in thousands, except for per share data):


	2017 Quarters
	First			Second			Third			Fourth
Net revenue	$	835,597		$	842,944		$	868,951		$	910,820

Operating expenses:
Practice salaries and benefits		572,385			561,418			586,476			617,455
Practice supplies and other operating expenses		27,796			30,872			29,497			32,353
General and administrative expenses		103,765			103,015			101,430			108,895
Depreciation and amortization		25,614			25,735			25,116			26,414

Total operating expenses		729,560			721,040			742,519			785,117

Income from operations		106,037			121,904			126,432			125,703
Investment and other income		576			365			235			2,777
Interest expense		(17,752	)		(18,535	)		(18,428	)		(19,844	)
Equity (losses) in earnings of unconsolidated affiliate		797			689			(240	)		(294	)

Total non-operating expenses		(16,379	)		(17,481	)		(18,433	)		(17,361	)
Income before income taxes		89,658			104,423			107,999			108,342
Income tax (provision) benefit		(34,967	)		(40,725	)		(42,119	)		27,761

Net income attributable to MEDNAX, Inc.	$	54,691		$	63,698		$	65,880		$	136,103

Per common and common equivalent share data (1):
Net income attributable to MEDNAX, Inc.:
Basic	$	0.59		$	0.69		$	0.71		$	1.47

Diluted	$	0.59		$	0.69		$	0.71		$	1.46

Weighted average common shares:
Basic		92,360			92,181			92,589			92,756

Diluted		93,143			92,812			92,881			93,159

(1)	Basic and diluted per share amounts are computed for each of the periods presented. Accordingly, the sum of the quarterly per share amounts may not agree with the full year amount.


	2016 Quarters
	First			Second			Third			Fourth
Net revenue	$	752,624		$	771,759		$	828,006		$	830,770

Operating expenses:
Practice salaries and benefits		491,811			484,625			521,832			532,952
Practice supplies and other operating expenses		27,046			26,992			31,641			32,737
General and administrative expenses		89,950			92,116			93,457			97,049
Depreciation and amortization		19,584			20,241			24,185			25,254

Total operating expenses		628,391			623,974			671,115			687,992

Income from operations		124,233			147,785			156,891			142,778
Investment and other income		618			410			221			770
Interest expense		(14,463	)		(15,058	)		(17,215	)		(16,356	)
Equity in earnings of unconsolidated affiliate		794			789			796			806

Total non-operating expenses		(13,051	)		(13,859	)		(16,198	)		(14,780	)
Income before income taxes		111,182			133,926			140,693			127,998
Income tax provision		(43,411	)		(51,601	)		(44,272	)		(49,919	)

Net income		67,771			82,325			96,421			78,079
Net loss attributable to noncontrolling interests		128			102			88			—

Net income attributable to MEDNAX, Inc.	$	67,899		$	82,427		$	96,509		$	78,079

Per common and common equivalent share data (2):
Net income attributable to MEDNAX, Inc.:
Basic	$	0.74		$	0.89		$	1.04		$	0.84

Diluted	$	0.73		$	0.89		$	1.04		$	0.84

Weighted average common shares:
Basic		92,269			92,182			92,604			92,728

Diluted		93,091			92,945			93,146			93,347

(2)	Basic and diluted per share amounts are computed for each of the periods presented. Accordingly, the sum of the quarterly per share amounts may not agree with the full year amount.

Schedule II: Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

Schedule II: Valuation and Qualifying Accounts

MEDNAX, INC.

Schedule II: Valuation and Qualifying Accounts


	Years Ended December 31,
	2017			2016			2015
Allowance for contractual adjustments and uncollectibles:
Balance at beginning of year	$	1,224,366		$	1,129,301		$	848,767
Amount charged against operating revenue		8,285,317			7,464,030			6,389,195
Accounts receivable contractual adjustments and write-offs (net of recoveries)		(8,223,648	)		(7,368,965	)		(6,108,661	)

Balance at end of year	$	1,286,035		$	1,224,366		$	1,129,301

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Principles of Presentation

Principles of Presentation

Recently Adopted Accounting Pronouncements

Recently Adopted Accounting Pronouncements

New Accounting Pronouncements

New Accounting Pronouncements

Accounting Estimates and Assumptions

Accounting Estimates and Assumptions

Segment Reporting

Segment Reporting

The following table summarizes the Company’s net revenue by service line (in percentages):


	Years Ended December 31,
	2017			2016			2015
Anesthesiology		38	%		39	%		37	%
Neonatology and other pediatric subspecialties		37	%		39	%		44	%
Maternal-fetal medicine		8	%		8	%		9	%
Radiology and teleradiology		8	%		6	%		4	%
Management services		6	%		5	%		2	%
Pediatric cardiology		3	%		3	%		4	%

		100	%		100	%		100	%

Revenue Recognition

Revenue Recognition

Cash and Cash Equivalents

Cash and Cash Equivalents

Certain cash equivalents carried by the Company are subject to the fair value provisions of the accounting guidance for fair value measurements. See “Fair Value Measurements” below.

Restricted Cash

Restricted Cash

Investments

Investments

Property and Equipment

Property and Equipment

Business Acquisitions

Business Acquisitions

Goodwill and Other Intangible Assets

Goodwill and Other Intangible Assets

Long-Lived Assets

Long-Lived Assets

Common Stock Repurchases

Common Stock Repurchases

Professional Liability Coverage

Professional Liability Coverage

Income Taxes

Income Taxes

Stock Incentive Plans

Stock Incentive Plans

Net Income Per Common Share

Net Income Per Common Share

Fair Value Measurements

Fair Value Measurements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of Net Revenue by Service Line

The following table summarizes the Company’s net revenue by service line (in percentages):


	Years Ended December 31,
	2017			2016			2015
Anesthesiology		38	%		39	%		37	%
Neonatology and other pediatric subspecialties		37	%		39	%		44	%
Maternal-fetal medicine		8	%		8	%		9	%
Radiology and teleradiology		8	%		6	%		4	%
Management services		6	%		5	%		2	%
Pediatric cardiology		3	%		3	%		4	%

		100	%		100	%		100	%

Investments (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

Investments held are summarized as follows (in thousands):


	December 31, 2017				December 31, 2016
	Short-Term		Long-Term		Short-Term		Long-Term
Municipal debt securities	$	8,312	$	46,195	$	10,306	$	46,513
Federal home loan securities		1,000		30,322		—		28,747
Certificates of deposit		980		4,165		980		3,715

	$	10,292	$	80,682	$	11,286	$	78,975

Schedule of Contractual Maturities of Long-Term Investments

Contractual maturities of long-term investments are summarized as follows (in thousands):


	December 31,
	2017		2016
Due after one year through five years	$	78,561	$	70,005
Due after five years through six years		2,121		8,970

	$	80,682	$	78,975

- Definition

Tabular disclosure of all investments in certain debt and equity securities for which the entity has the positive intent and ability to hold until maturity.

+ References + Details

Accounts Receivable and Net Revenue (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Schedule of Accounts Receivable, Net

Accounts receivable, net consists of the following (in thousands):


	December 31,
	2017			2016
Gross accounts receivable	$	1,790,034		$	1,719,642
Allowance for contractual adjustments and uncollectibles		(1,286,035	)		(1,224,366	)

	$	503,999		$	495,276

Schedule of Net Revenue

Net revenue consists of the following (in thousands):


	Years Ended December 31,
	2017			2016			2015
Gross revenue	$	11,427,238		$	10,374,813		$	8,942,957
Contractual adjustments and uncollectibles		(8,285,317	)		(7,464,030	)		(6,389,195	)
Hospital contract administrative fees		316,391			272,376			226,234

	$	3,458,312		$	3,183,159		$	2,779,996

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment consists of the following (in thousands):


	December 31,
	2017			2016
Building	$	33,024		$	26,572
Land		6,683			6,683
Equipment and other		253,453			213,521

		293,160			246,776
Accumulated depreciation		(169,624	)		(143,708	)

	$	123,536		$	103,068

Business Acquisitions (Tables)

12 Months Ended

Dec. 31, 2017

Business Combinations [Abstract]

Summary of Company's Preliminary Allocation of Purchase Price

The Company’s preliminary allocation of purchase price is as follows (in thousands):


Current assets	$	43,550
Property and equipment		5,281
Other noncurrent assets		52,611
Goodwill		439,822
Other intangible assets		39,414
Current liabilities		(5,674	)
Other long-term liabilities		(21,086	)

	$	553,918

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Intangible Assets, Net

Intangible assets, net, consist of the following (in thousands):


	December 31, 2017
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Physician and hospital agreements	$	381,635	$	(203,915	)	$	177,720
Customer relationships		443,300		(48,837	)		394,463
Trade names		43,156		(2,933	)		40,223
Patented and other technology		38,590		(11,068	)		27,522

	$	906,681	$	(266,753	)	$	639,928


	December 31, 2016
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Physician and hospital agreements	$	347,862	$	(168,488	)	$	179,374
Customer relationships		443,300		(27,368	)		415,932
Trade names		43,156		(1,604	)		41,552
Patented and other technology		37,503		(5,832	)		31,671

	$	871,821	$	(203,292	)	$	668,529

Amortization Expenses for Existing Intangible Assets for the Next Five Years

Amortization expense for existing intangible assets for the next five years is expected to be as follows (in thousands):


2018	$	67,514
2019		62,669
2020		56,636
2021		51,069
2022		44,357

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following (in thousands):


	December 31,
	2017		2016
Accounts payable	$	34,632	$	28,474
Accrued salaries and bonuses		225,429		220,635
Accrued payroll taxes and benefits		75,672		67,830
Accrued professional liabilities		37,912		28,972
Accrued contingent consideration		6,259		6,566
Accrued interest		4,495		4,511
Other accrued expenses		53,618		50,950

	$	438,017	$	407,938

Accrued Professional Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Health Care Organizations [Abstract]

Schedule of Accrued Professional Liability

The activity related to the Company’s total accrued professional liability for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands):


	Years Ended December 31,
	2017			2016			2015
Balance at beginning of year	$	202,052		$	202,527		$	168,369
Assumed liabilities through acquisition		20,716			—			35,968
Provision (adjustment) for losses related to:
Current year		41,291			38,129			39,204
Prior years		9,983			(25,428	)		(25,797	)

Total provision for losses		51,274			12,701			13,407
Claim payments related to:
Current year		(712	)		(766	)		(1,382	)
Prior years		(23,143	)		(12,410	)		(13,835	)

Total payments		(23,855	)		(13,176	)		(15,217	)

Balance at end of year	$	250,187		$	202,052		$	202,527

Line of Credit, Long-Term Debt and Capital Lease Obligations (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Long-Term Debt

The carrying value of the Company’s long-term debt was $1.8 billion and $1.7 billion at December 31, 2017 and 2016, respectively, and consisted of the following (in thousands):


	December 31, 2017
	Principal		Unamortized Debt Issuance Costs			Total
2023 Senior Notes	$	750,000	$	(9,503	)	$	740,497
Revolving line of credit		1,110,500		(4,864	)		1,105,636

Total	$	1,860,500	$	(14,367	)	$	1,846,133


	December 31, 2016
	Principal			Unamortized Debt Issuance Costs			Total
2023 Senior Notes	$	750,000		$	(11,109	)	$	738,891
Revolving line of credit		783,500			(3,388	)		780,112
Term loan		180,000			(259	)		179,741

		1,713,500			(14,756	)		1,698,744
Less: Current portion		(20,000	)		—			(20,000	)

Long-term portion	$	1,693,500		$	(14,756	)	$	1,678,744

Schedule of Capital Lease Obligations

The Company’s capital lease obligations consist of the following (in thousands):


	December 31,
	2017			2016
Capital lease obligations	$	1,826		$	3,550
Less: Current portion		(1,401	)		(2,054	)

Long-term portion	$	425		$	1,496

Schedule of Amounts Due Under Terms of Capital Lease Obligations

The amounts due under the terms of the Company’s capital lease obligations at December 31, 2017 are as follows:


2018	$	1,401
2019		238
2020		113
2021		74

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Summary of Components of Income Tax Provision

The components of the income tax provision (benefit) are as follows (in thousands):


	December 31,
	2017			2016		2015
Federal:
Current	$	130,053		$	166,758	$	168,596
Deferred		(63,038	)		15,596		12,866

		67,015			182,354		181,462

State:
Current		20,070			4,296		20,948
Deferred		2,965			2,553		1,628

		23,035			6,849		22,576

Total	$	90,050		$	189,203	$	204,038

Schedule of Differences Between Effective Rate and United States Federal Income Tax Statutory Rate

The differences between the effective rate and the United States federal income tax statutory rate are as follows:


	December 31,
	2017			2016			2015
Tax at statutory rate		35.00	%		35.00	%		35.00	%
State income tax, net of federal benefit		3.33			2.94			2.97
Non-deductible expenses		0.49			0.43			0.34
Change in accrual estimates relating to uncertain tax positions		0.02			(2.11	)		(0.43	)
Change in valuation allowance		—			0.48			0.29
Other, net		0.16			0.06			(0.41	)
Change in tax law		(17.06	)		—			—

Income tax provision		21.94	%		36.80	%		37.76	%

Significant Components of Deferred Income Tax Assets and Liabilities

All of the Company’s deferred tax assets and liabilities are classified as long-term. The significant components of deferred income tax assets and liabilities are as follows (in thousands):


	December 31,
	2017			2016
Allowance for uncollectible accounts	$	80,056		$	103,525
Reserves and accruals		45,454			62,212
Stock-based compensation		7,975			13,726
Net operating loss carryforward		28,569			49,156
Property and equipment		685			1,621
Other		970			1,610

Deferred tax assets before valuation allowance		163,709			231,850
Less: Valuation allowance		(2,615	)		(4,014	)

Deferred tax assets, net of valuation allowance		161,094			227,836

Gross deferred tax liabilities:
Amortization		(258,618	)		(380,594	)
Accrual to cash adjustment		(31,290	)		(53,771	)
Other		(4,150	)		(1,023	)

Total deferred tax liabilities		(294,058	)		(435,388	)

Net deferred tax liability	$	(132,964	)	$	(207,552	)

Schedule of Activity Related to Gross Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s liability for uncertain tax positions for the years ended December 31, 2017, 2016 and 2015 (in thousands):


	Years Ended December 31,
	2017			2016			2015
Balance at beginning of year	$	9,469		$	18,447		$	17,165
Increases related to prior year tax positions		2,284			301			467
Decreases related to prior year tax positions		(143	)		(3,927	)		(1,168	)
Increases related to current year tax positions		1,430			2,258			3,675
Settlements		—			(5,644	)		—
Decreases related to lapse of statutes of limitation		(2,068	)		(1,966	)		(1,692	)

Balance at end of year	$	10,972		$	9,469		$	18,447

Common and Common Equivalent Shares (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Calculation of Shares Used in Basic and Diluted Net Income Per Share

The calculation of shares used in the basic and diluted net income per share calculation for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands):


	Years Ended December 31,
	2017		2016		2015
Weighted average number of common shares outstanding		92,431		92,422		93,077
Weighted average number of dilutive common share equivalents		527		687		883

Weighted average number of common and common equivalent shares outstanding		92,958		93,109		93,960

Antidilutive securities not included in the diluted net income per common share calculation		107		2		—

Stock Incentive Plans and Stock Purchase Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Restricted Stock and Deferred Stock Awards

The activity related to the Company’s restricted stock and deferred stock awards and the corresponding weighted average grant-date fair values for the year ended December 31, 2017 are as follows:


	Number of Shares			Weighted Average Fair Value
Non-vested shares at January 1, 2017		946,329		$	66.98
Awarded		637,529		$	54.22
Forfeited		(91,730	)	$	64.82
Vested		(451,094	)	$	65.00

Non-vested shares at December 31, 2017		1,041,034		$	60.21

Schedule of Activity and Certain Other Information Related to Stock Option Awards

The activity and certain other information related to the Company’s outstanding stock option awards for the year ended December 31, 2017 are as follows:


	Number of Stock Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at January 1, 2017		410,286		$	28.33
Exercised		(163,944	)	$	29.57			$	5.5

Outstanding and exercisable at December 31, 2017		246,342		$	27.51		1.5	$	6.4

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments under Non-Cancelable Operating Leases

Future minimum lease payments under non-cancelable operating leases as of December 31, 2017 are as follows (in thousands):


2018	$	34,337
2019		24,178
2020		16,633
2021		12,065
2022		8,125
Thereafter		9,934

	$	105,272

Selected Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Summary of Company's Selected Quarterly Financial Information


	2017 Quarters
	First			Second			Third			Fourth
Net revenue	$	835,597		$	842,944		$	868,951		$	910,820

Operating expenses:
Practice salaries and benefits		572,385			561,418			586,476			617,455
Practice supplies and other operating expenses		27,796			30,872			29,497			32,353
General and administrative expenses		103,765			103,015			101,430			108,895
Depreciation and amortization		25,614			25,735			25,116			26,414

Total operating expenses		729,560			721,040			742,519			785,117

Income from operations		106,037			121,904			126,432			125,703
Investment and other income		576			365			235			2,777
Interest expense		(17,752	)		(18,535	)		(18,428	)		(19,844	)
Equity (losses) in earnings of unconsolidated affiliate		797			689			(240	)		(294	)

Total non-operating expenses		(16,379	)		(17,481	)		(18,433	)		(17,361	)
Income before income taxes		89,658			104,423			107,999			108,342
Income tax (provision) benefit		(34,967	)		(40,725	)		(42,119	)		27,761

Net income attributable to MEDNAX, Inc.	$	54,691		$	63,698		$	65,880		$	136,103

Per common and common equivalent share data (1):
Net income attributable to MEDNAX, Inc.:
Basic	$	0.59		$	0.69		$	0.71		$	1.47

Diluted	$	0.59		$	0.69		$	0.71		$	1.46

Weighted average common shares:
Basic		92,360			92,181			92,589			92,756

Diluted		93,143			92,812			92,881			93,159

(1)	Basic and diluted per share amounts are computed for each of the periods presented. Accordingly, the sum of the quarterly per share amounts may not agree with the full year amount.


	2016 Quarters
	First			Second			Third			Fourth
Net revenue	$	752,624		$	771,759		$	828,006		$	830,770

Operating expenses:
Practice salaries and benefits		491,811			484,625			521,832			532,952
Practice supplies and other operating expenses		27,046			26,992			31,641			32,737
General and administrative expenses		89,950			92,116			93,457			97,049
Depreciation and amortization		19,584			20,241			24,185			25,254

Total operating expenses		628,391			623,974			671,115			687,992

Income from operations		124,233			147,785			156,891			142,778
Investment and other income		618			410			221			770
Interest expense		(14,463	)		(15,058	)		(17,215	)		(16,356	)
Equity in earnings of unconsolidated affiliate		794			789			796			806

Total non-operating expenses		(13,051	)		(13,859	)		(16,198	)		(14,780	)
Income before income taxes		111,182			133,926			140,693			127,998
Income tax provision		(43,411	)		(51,601	)		(44,272	)		(49,919	)

Net income		67,771			82,325			96,421			78,079
Net loss attributable to noncontrolling interests		128			102			88			—

Net income attributable to MEDNAX, Inc.	$	67,899		$	82,427		$	96,509		$	78,079

Per common and common equivalent share data (2):
Net income attributable to MEDNAX, Inc.:
Basic	$	0.74		$	0.89		$	1.04		$	0.84

Diluted	$	0.73		$	0.89		$	1.04		$	0.84

Weighted average common shares:
Basic		92,269			92,182			92,604			92,728

Diluted		93,091			92,945			93,146			93,347

(2)	Basic and diluted per share amounts are computed for each of the periods presented. Accordingly, the sum of the quarterly per share amounts may not agree with the full year amount.

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 08, 2015
Summary Of Significant Accounting Policies [Line Items]
Sale of minority interest percentage	75.00%
Cash and cash equivalents maturity description		90
Additional amounts to be paid in cash or common stock based on achievement of performance measures within period, maximum years		5 years
Money market funds fair value		$ 9.2	$ 12.4
Cash surrender fair value of life insurance		15.6	15.8
Contingent consideration liabilities related to acquisitions		$ 30.5	$ 17.3
5.25% Senior Unsecured Notes Due 2023 [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument interest rate				5.25%
Unnamed Corporate Joint Venture [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method ownership percentage in joint venture		37.50%
Government Contracts Concentration Risk [Member] \| Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of net accounts receivable		17.00%	17.00%
Buildings [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		30 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Long-term investments maturity period, in years		6 years
Short-Term investments maturity period, in years		1 year
Intangible assets finite lives		20 years
Maximum [Member] \| Medical Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		7 years
Maximum [Member] \| Computer Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		7 years
Maximum [Member] \| Software and Software Development Costs [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		7 years
Maximum [Member] \| Furniture [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		7 years
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Long-term investments maturity period, in years		1 year
Intangible assets finite lives		1 year
Minimum [Member] \| Medical Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		3 years
Minimum [Member] \| Computer Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		3 years
Minimum [Member] \| Software and Software Development Costs [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		3 years
Minimum [Member] \| Furniture [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives, years		3 years

Summary of Significant Accounting Policies - Schedule of Net Revenue by Service Line (Detail) - Product Concentration Risk [Member] - Sales Revenue, Services, Net [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net revenue in percentage	100.00%	100.00%	100.00%
Anesthesiology [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	38.00%	39.00%	37.00%
Neonatology and Other Pediatric Subspecialties [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	37.00%	39.00%	44.00%
Maternal-Fetal Medicine [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	8.00%	8.00%	9.00%
Radiology And Teleradiology [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	8.00%	6.00%	4.00%
Management Services [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	6.00%	5.00%	2.00%
Pediatric Cardiology [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	3.00%	3.00%	4.00%

Investments - Schedule of Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	$ 10,292	$ 11,286
Long-Term	80,682	78,975
Municipal Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	8,312	10,306
Long-Term	46,195	46,513
Federal Home Loan Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	1,000
Long-Term	30,322	28,747
Certificates of Deposit [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	980	980
Long-Term	$ 4,165	$ 3,715

Investments - Schedule of Contractual Maturities of Long-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Due after one year through five years	$ 78,561	$ 70,005
Due after five years through six years	2,121	8,970
Total	$ 80,682	$ 78,975

Accounts Receivable and Net Revenue - Schedule of Accounts Receivable, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Gross accounts receivable	$ 1,790,034	$ 1,719,642
Allowance for contractual adjustments and uncollectibles	(1,286,035)	(1,224,366)
Accounts receivable, net	$ 503,999	$ 495,276

Accounts Receivable and Net Revenue - Schedule of Net Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Gross revenue									$ 11,427,238	$ 10,374,813	$ 8,942,957
Contractual adjustments and uncollectibles									(8,285,317)	(7,464,030)	(6,389,195)
Hospital contract administrative fees									316,391	272,376	226,234
Net revenue	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 830,770	$ 828,006	$ 771,759	$ 752,624	$ 3,458,312	$ 3,183,159	$ 2,779,996

Accounts Receivable and Net Revenue - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Accounts receivable, net	$ 503,999				$ 495,276				$ 503,999	$ 495,276
Net patient service revenue	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 830,770	$ 828,006	$ 771,759	$ 752,624	$ 3,458,312	$ 3,183,159	$ 2,779,996

Property Plant and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Building	$ 33,024	$ 26,572
Land	6,683	6,683
Equipment and other	253,453	213,521
Property and equipment, gross	293,160	246,776
Accumulated depreciation	(169,624)	(143,708)
Property and equipment, net	$ 123,536	$ 103,068

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Medical and other equipment held under capital leases	$ 293,160	$ 246,776
Accumulated depreciation of property and equipment held under capital leases	169,624	143,708
Recorded depreciation expense	33,900	29,000	$ 22,200
Medical and Other Equipment Held under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Medical and other equipment held under capital leases	6,100	6,200
Accumulated depreciation of property and equipment held under capital leases	$ 4,600	$ 4,000

Business Acquisitions - Additional Information (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017 USD ($) Company shares	Dec. 31, 2016 USD ($) Company Acquisition
Business Acquisition [Line Items]
Number of physician group practices acquired \| Company		10	13
Number of neonatology practices acquired \| Company		1	1
Number of maternal-fetal medicine practices acquired \| Company		2	1
Number of other pediatric subspecialty practices acquired \| Company		2	2
Number of pediatric multi-specialty practice acquired \| Company		1
Number of radiology practices acquired \| Company		4
Total business acquisition consideration, net of cash acquired		$ 554,000	$ 759,600
Cash payments to acquire businesses		531,700	756,100
Payments to acquire business by issue of common stock		$ 2,700
Number of shares of common stock issued \| shares		69,014
Contingent consideration liability		$ 18,600	$ 3,500
Purchase consideration liability		$ 1,000
Contractual restriction period on disposition or assignment of common stock		3 years
Assets held for sale, current		$ 23,500
Assets held for sale, other noncurrent assets		$ 22,500
Business combination contingent consideration arrangements description		The contingent consideration of $18.6 million recorded during the year ended December 31, 2017 is related to an agreement to pay an additional cash amount based on the achievement of certain performance measures for the period through June 1, 2019.
Restricted cash		$ 20,000
Contingent consideration payments related to prior-period acquisitions		6,200
Number of business acquired \| Acquisition			15
Cash acquired from acquisition			$ 15,000
Number of third-party receivables companies acquired \| Company			1
Number of anesthesiology practices acquired \| Company			8
Number of pediatric cardiology practices acquired \| Company			1
Number of patient engagement software company acquired \| Company			1
Sale of minority interest percentage	75.00%
Deconsolidation percentage	100.00%
Prior-Period Acquisitions [Member]
Business Acquisition [Line Items]
Increase in deferred tax liabilities		500
Increase in goodwill resulting from finalization of tax acquisition accounting		500
Contingent Consideration [Member]
Business Acquisition [Line Items]
Range of the undiscounted amount under contingent consideration agreement, low		0
Range of the undiscounted amount under contingent consideration agreement, high		20,000
Restricted cash		$ 20,000
Minimum [Member] \| Contingent Consideration [Member]
Business Acquisition [Line Items]
Assumed discount rates for acquisition-date fair value		4.00%
Maximum [Member] \| Contingent Consideration [Member]
Business Acquisition [Line Items]
Assumed discount rates for acquisition-date fair value		4.75%

Business Acquisitions - Summary of Company's Preliminary Allocation of Purchase Price (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 4,283,963	$ 3,845,157
Physician Group [Member]
Business Acquisition [Line Items]
Current assets	43,550
Property and equipment	5,281
Other noncurrent assets	52,611
Goodwill	439,822
Other intangible assets	39,414
Current liabilities	(5,674)
Other long-term liabilities	(21,086)
Total assets and liabilities	$ 553,918

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 4,283,963	$ 3,845,157
Change in goodwill carrying amount	438,800
Goodwill deductible for tax purpose	159,500
Intangible assets related to acquisitions	39,400
Amortization expense for intangible assets	$ 68,900	$ 60,300	$ 42,000
Physician And Hospital Agreements [Member]
Goodwill And Other Intangible Assets [Line Items]
Weighted average amortization period	10 years

Goodwill and Intangible Assets - Summary of Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 906,681	$ 871,821
Accumulated Amortization	(266,753)	(203,292)
Net Carrying Value	639,928	668,529
Physician And Hospital Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	381,635	347,862
Accumulated Amortization	(203,915)	(168,488)
Net Carrying Value	177,720	179,374
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	443,300	443,300
Accumulated Amortization	(48,837)	(27,368)
Net Carrying Value	394,463	415,932
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	43,156	43,156
Accumulated Amortization	(2,933)	(1,604)
Net Carrying Value	40,223	41,552
Patented and Other Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	38,590	37,503
Accumulated Amortization	(11,068)	(5,832)
Net Carrying Value	$ 27,522	$ 31,671

Goodwill and Intangible Assets - Amortization Expenses for Existing Intangible Assets for the Next Five Years (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for existing other intangible assets, 2018	$ 67,514
Amortization expense for existing other intangible assets, 2019	62,669
Amortization expense for existing other intangible assets, 2020	56,636
Amortization expense for existing other intangible assets, 2021	51,069
Amortization expense for existing other intangible assets, 2022	$ 44,357

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable	$ 34,632	$ 28,474
Accrued salaries and bonuses	225,429	220,635
Accrued payroll taxes and benefits	75,672	67,830
Accrued professional liabilities	37,912	28,972
Accrued contingent consideration	6,259	6,566
Accrued interest	4,495	4,511
Other accrued expenses	53,618	50,950
Accounts payable and accrued expenses, total	$ 438,017	$ 407,938

Accrued Professional Liabilities - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Total accrued professional liability	$ 250,187	$ 202,052	$ 202,527	$ 168,369
Accrued professional liability incurred but loss reserves not reported for claims	138,500	128,100
Accrued professional liability incurred and loss reserves reported for claims	111,700	74,000
Accrued professional liabilities	37,912	$ 28,972
Insurance receivables	$ 18,900

Accrued Professional Liabilities - Schedule of Accrued Professional Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Balance at beginning of year	$ 202,052	$ 202,527	$ 168,369
Assumed liabilities through acquisition	20,716		35,968
Provision (adjustment) for losses related to Current year	41,291	38,129	39,204
Provision (adjustment) for losses related to Prior years	9,983	(25,428)	(25,797)
Total provision for losses	51,274	12,701	13,407
Claim payments related to Current year	(712)	(766)	(1,382)
Claim payments related to Prior years	(23,143)	(12,410)	(13,835)
Total payments	(23,855)	(13,176)	(15,217)
Balance at end of year	$ 250,187	$ 202,052	$ 202,527

Line of Credit, Long-Term Debt and Capital Lease Obligations - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 08, 2015
Debt Instrument [Line Items]
Line of Credit facility, maturity date	Oct. 31, 2022
Long term debt	$ 1,846,133,000	$ 1,698,744,000
Letters of credit outstanding amount	200,000
Line of Credit facility, available balance	$ 889,300,000
Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.15%
Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.30%
Alternate Base Rate [Member] \| Federal Funds Rate [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	Federal Funds Rate plus 1/2 of 1.00%
Alternate Base Rate [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	LIBOR for an interest period of one month plus 1.00%
Debt instrument, variable interest rate	1.00%
Applicable Margin Rate [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate	0.125%
Applicable Margin Rate [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate	0.75%
Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit facility, borrowing capacity	$ 2,000,000,000
Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit facility, borrowing capacity	$ 37,500,000
5.25% Senior Unsecured Notes Due 2023 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt			$ 750,000,000
Debt instrument interest rate			5.25%
Debt instrument maturity date description	Payable semi-annually in arrears on June 1 and December 1
Debt instrument, maturity year	2023
Long term debt	$ 740,497,000	738,891,000
Estimated fair value of notes	$ 763,100,000	$ 773,400,000
5.25% Senior Unsecured Notes Due 2023 [Member] \| Change In Control [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.00%
5.25% Senior Unsecured Notes Due 2023 [Member] \| Redemption Before 2018 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	100.00%
5.25% Senior Unsecured Notes Due 2023 [Member] \| Redemption Before 2018 [Member] \| Redeem up to 35% of Aggregate Principal Amount [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	35.00%
Redemption price percentage of aggregate principal amount redeemed	105.25%
5.25% Senior Unsecured Notes Due 2023 [Member] \| Redemption in 2018 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	103.938%
5.25% Senior Unsecured Notes Due 2023 [Member] \| Redemption in 2019[Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	102.625%
5.25% Senior Unsecured Notes Due 2023 [Member] \| Redemption in 2020 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.313%
5.25% Senior Unsecured Notes Due 2023 [Member] \| Redemption in 2021 and Thereafter [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	100.00%

Line of Credit, Long-Term Debt and Capital Lease Obligations - Schedule of Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt instrument principal amount	$ 1,860,500	$ 1,713,500
Less: Current portion, principal		(20,000)
Debt instrument principal long-term portion		1,693,500
Unamortized debt issuance cost	(14,367)	(14,756)
Less: Current portion, unamortized debt issuance costs		0
Long-term portion, principal, unamortized debt issuance costs		(14,756)
Long term debt	1,846,133	1,698,744
Less: Current portion		(20,000)
Long-term portion		1,678,744
5.25% Senior Unsecured Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	750,000	750,000
Unamortized debt issuance cost	(9,503)	(11,109)
Long term debt	740,497	738,891
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	1,110,500	783,500
Unamortized debt issuance cost	(4,864)	(3,388)
Long term debt	$ 1,105,636	780,112
Term Loan Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument principal amount		180,000
Unamortized debt issuance cost		(259)
Long term debt		$ 179,741

Line of Credit, Long-Term Debt and Capital Lease Obligations - Schedule of Capital Lease Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Capital lease obligations	$ 1,826	$ 3,550
Less: Current portion	(1,401)	(2,054)
Long-term portion	$ 425	$ 1,496

Line of Credit, Long-Term Debt and Capital Lease Obligations - Schedule of Amounts Due Under Terms of Capital Lease Obligations (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Debt Disclosure [Abstract]
2018	$ 1,401
2019	238
2020	113
2021	$ 74

Income Taxes - Summary of Components of Income Tax Provision (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal, Current									$ 130,053	$ 166,758	$ 168,596
Federal, Deferred									(63,038)	15,596	12,866
Federal income tax provision, Total									67,015	182,354	181,462
State, Current									20,070	4,296	20,948
State, Deferred									2,965	2,553	1,628
State income tax provision, Total									23,035	6,849	22,576
Income tax provision, Total	$ (27,761)	$ 42,119	$ 40,725	$ 34,967	$ 49,919	$ 44,272	$ 51,601	$ 43,411	$ 90,050	$ 189,203	$ 204,038

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Effective tax rate									21.94%	36.80%	37.76%
Income tax benefit resulting from the reduction of deferred tax liabilities	$ (70,000)								$ (70,000)
Effective tax rate excluding impact of income tax benefit									39.00%
Effective income tax rate favorable impact of change in uncertain tax positions						$ 10,600
Effective tax rate excluding impact of tax settlement										38.87%	37.76%
Increase (decrease) in net deferred tax liability									$ (74,600)
Adjustment to additional paid-in capital for excess tax benefits related to stock-based awards										$ 4,200	$ 11,600
Income tax expense for excess tax deficiencies									200
Net operating loss carryforwards for federal and state tax	116,000				$ 130,000				116,000	130,000	136,600
Uncertain tax position liability	10,972				9,469				10,972	9,469	18,447	$ 17,165
Unrecognized tax benefits that would impact effective tax rate	10,700								10,700
Increase (decrease) in uncertain tax position									1,500	(9,000)
Expected decrease in uncertain tax position in the next twelve months	1,100								1,100
Income tax expense (benefit)	(27,761)	$ 42,119	$ 40,725	$ 34,967	49,919	$ 44,272	$ 51,601	$ 43,411	90,050	189,203	204,038
Company's accrued liability for interest and penalties related to income tax liabilities	$ 1,200				$ 1,400				1,200	1,400
Interest and Penalties [Member]
Income Tax [Line Items]
Income tax expense (benefit)									$ (200)	$ (7,900)	$ 600
Earliest Tax Year [Member]
Income Tax [Line Items]
Federal and state income tax examinations									2013
Latest Tax Year [Member]
Income Tax [Line Items]
Federal and state income tax examinations										2016
Minimum [Member]
Income Tax [Line Items]
Expiration period of operating loss carryforwards									2019
Maximum [Member]
Income Tax [Line Items]
Expiration period of operating loss carryforwards									2037

Income Taxes - Schedule of Differences Between Effective Rate and United States Federal Income Tax Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal benefit	3.33%	2.94%	2.97%
Non-deductible expenses	0.49%	0.43%	0.34%
Change in accrual estimates relating to uncertain tax positions	0.02%	(2.11%)	(0.43%)
Change in valuation allowance		0.48%	0.29%
Other, net	0.16%	0.06%	(0.41%)
Change in tax law	(17.06%)
Income tax provision	21.94%	36.80%	37.76%

Income Taxes - Significant Components of Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Allowance for uncollectible accounts	$ 80,056	$ 103,525
Reserves and accruals	45,454	62,212
Stock-based compensation	7,975	13,726
Net operating loss carryforward	28,569	49,156
Property and equipment	685	1,621
Other	970	1,610
Deferred tax assets before valuation allowance	163,709	231,850
Less: Valuation allowance	(2,615)	(4,014)
Deferred tax assets, net of valuation allowance	161,094	227,836
Gross deferred tax liabilities:
Amortization	(258,618)	(380,594)
Accrual to cash adjustment	(31,290)	(53,771)
Other	(4,150)	(1,023)
Total deferred tax liabilities	(294,058)	(435,388)
Net deferred tax liability	$ (132,964)	$ (207,552)

Income Taxes - Schedule of Activity Related to Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 9,469	$ 18,447	$ 17,165
Increases related to prior year tax positions	2,284	301	467
Decreases related to prior year tax positions	(143)	(3,927)	(1,168)
Increases related to current year tax positions	1,430	2,258	3,675
Settlements		(5,644)
Decreases related to lapse of statutes of limitation	(2,068)	(1,966)	(1,692)
Balance at end of year	$ 10,972	$ 9,469	$ 18,447

Common and Common Equivalent Shares - Schedule of Calculation of Shares Used in Basic and Diluted Net Income Per Share (Detail) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Weighted average number of common shares outstanding	92,756	92,589	92,181	92,360	92,728	92,604	92,182	92,269	92,431	92,422	93,077
Weighted average number of dilutive common share equivalents									527	687	883
Weighted average number of common and common equivalent shares outstanding	93,159	92,881	92,812	93,143	93,347	93,146	92,945	93,091	92,958	93,109	93,960
Antidilutive securities not included in the diluted net income per common share calculation									107	2

Stock Incentive Plans and Stock Purchase Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, aggregate shares authorized	200,000,000	200,000,000
Stock-based compensation expense related to its stock incentive plans, ESPP and SPP	$ 29,600,000	$ 34,000,000	$ 32,100,000
Aggregate fair value of restricted and deferred stocks vested	$ 29,300,000	$ 29,800,000	$ 31,600,000
Weighted average grant-date fair value of restricted and deferred stock awards granted	$ 54.22	$ 67.90	$ 70.44
Aggregate intrinsic value of stock options exercised	$ 5,500,000	$ 6,800,000	$ 11,300,000
Excess tax benefit related to employee stock incentive plans	0	4,131,000	11,583,000
Cash proceeds received from the exercise of stock options	$ 4,800,000	$ 4,700,000	$ 6,100,000
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of options, maximum years	10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Restricted and Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to non-vested restricted stock, weighted-average period in years	1 year 7 months 6 days
Unrecognized compensation expense related to non-vested restricted shares	$ 30,900,000
1996 Non-Qualified Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of market value of common stock at which employees are permitted to purchase	85.00%
2015 Non-Qualified Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of market value of common stock at which employees are permitted to purchase	90.00%
Amended and Restated 2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants and awards under Stock Incentive Plans	3,400,000
1996 Non-Qualified Employee Stock Purchase Plan and 2015 Non-Qualified Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number Shares issued under Stock Purchase Plans	400,000
Common stock, aggregate shares authorized	2,600,000
Common stock, reserved for issuance	1,900,000

Stock Incentive Plans and Stock Purchase Plans - Schedule of Restricted Stock and Deferred Stock Awards (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Non-vested shares at January 1, 2017	946,329
Number of Shares, Awarded	637,529
Number of Shares, Forfeited	(91,730)
Number of Shares, Vested	(451,094)
Number of Shares, Non-vested shares at December 31, 2017	1,041,034	946,329
Weighted Average Fair Value, Non-vested shares at January 1, 2017	$ 66.98
Weighted Average Fair Value, Awarded	54.22	$ 67.90	$ 70.44
Weighted Average Fair Value, Forfeited	64.82
Weighted Average Fair Value, Vested	65.00
Weighted Average Fair Value, Non-vested shares at December 31, 2017	$ 60.21	$ 66.98

Stock Incentive Plans and Stock Purchase Plans - Schedule of Activity and Certain Other Information Related to Stock Option Awards (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Outstanding at January 1, 2017	410,286
Number of Shares, Exercised	(163,944)
Number of Shares, Outstanding at December 31, 2017	246,342	410,286
Number of Shares, Exercisable at December 31, 2017	246,342
Weighted Average Exercise Price, Outstanding at January 1, 2017	$ 28.33
Weighted Average Exercise Price, Exercised	29.57
Weighted Average Exercise Price, Outstanding at December 31, 2017	27.51	$ 28.33
Weighted Average Exercise Price, Exercisable at December 31, 2017	$ 27.51
Weighted Average Remaining Contractual Term (in years), Outstanding at December 31, 2017	1 year 6 months
Weighted Average Remaining Contractual Term (in years), Exercisable at December 31, 2017	1 year 6 months
Aggregate Intrinsic Value, Exercised	$ 5.5	$ 6.8	$ 11.3
Aggregate Intrinsic Value, Outstanding at December 31, 2017	6.4
Aggregate Intrinsic Value, Exercisable at December 31, 2017	$ 6.4

Common Stock Repurchase Programs - Additional Information (Detail) - USD ($)			1 Months Ended		12 Months Ended
	Mar. 16, 2015	Dec. 17, 2014	Oct. 31, 2015	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Oct. 31, 2014
Common Stock [Line Items]
Common stock repurchased					$ 70,192,000	$ 61,828,000	$ 235,051,000
Common stock authorized for repurchase										$ 600,000,000
Common Stock [Member]
Common Stock [Line Items]
Repurchased common stock, shares					1,038,000	946,000	3,365,000
Common stock repurchased					$ 10,000	$ 9,000	$ 34,000
Restricted Stock [Member]
Common Stock [Line Items]
Number of shares withheld to satisfy minimum statutory tax withholding obligations					38,257	46,490
Amount withheld to satisfy minimum statutory tax withholding obligations					$ 2,100,000	$ 3,200,000
Accelerated Share Repurchase (ASR) Agreements [Member]
Common Stock [Line Items]
Repurchased common stock, shares	2,200,000	2,500,000	300,000	300,000
Common stock repurchased	$ 200,000,000	$ 200,000,000
Common stock purchase								$ 200,000,000	$ 200,000,000

Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2018	$ 34,337
2019	24,178
2020	16,633
2021	12,065
2022	8,125
Thereafter	9,934
Total	$ 105,272

Selected Quarterly Financial Information - Summary of Company's Selected Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 830,770	$ 828,006	$ 771,759	$ 752,624	$ 3,458,312	$ 3,183,159	$ 2,779,996
Practice salaries and benefits	617,455	586,476	561,418	572,385	532,952	521,832	484,625	491,811	2,337,734	2,031,220	1,753,505
Practice supplies and other operating expenses	32,353	29,497	30,872	27,796	32,737	31,641	26,992	27,046	120,518	118,416	98,480
General and administrative expenses	108,895	101,430	103,015	103,765	97,049	93,457	92,116	89,950	417,105	372,572	305,915
Depreciation and amortization	26,414	25,116	25,735	25,614	25,254	24,185	20,241	19,584	102,879	89,264	64,228
Total operating expenses	785,117	742,519	721,040	729,560	687,992	671,115	623,974	628,391	2,978,236	2,611,472	2,222,128
Income from operations	125,703	126,432	121,904	106,037	142,778	156,891	147,785	124,233	480,076	571,687	557,868
Investment and other income	2,777	235	365	576	770	221	410	618	3,953	2,019	1,844
Interest expense	(19,844)	(18,428)	(18,535)	(17,752)	(16,356)	(17,215)	(15,058)	(14,463)	(74,559)	(63,092)	(23,110)
Equity (losses) in earnings of unconsolidated affiliate	(294)	(240)	689	797	806	796	789	794	952	3,185	3,127
Total non-operating expenses	(17,361)	(18,433)	(17,481)	(16,379)	(14,780)	(16,198)	(13,859)	(13,051)	(69,654)	(57,888)	(18,139)
Income before income taxes	108,342	107,999	104,423	89,658	127,998	140,693	133,926	111,182	410,422	513,799	539,729
Income tax (provision) benefit	27,761	(42,119)	(40,725)	(34,967)	(49,919)	(44,272)	(51,601)	(43,411)	(90,050)	(189,203)	(204,038)
Net income					78,079	96,421	82,325	67,771	320,372	324,596	335,691
Net loss attributable to noncontrolling interests						88	102	128		318	629
Net income attributable to MEDNAX, Inc.	$ 136,103	$ 65,880	$ 63,698	$ 54,691	$ 78,079	$ 96,509	$ 82,427	$ 67,899	$ 320,372	$ 324,914	$ 336,320
Earnings per share, Basic	$ 1.47	$ 0.71	$ 0.69	$ 0.59	$ 0.84	$ 1.04	$ 0.89	$ 0.74	$ 3.47	$ 3.52	$ 3.61
Earnings per share, Diluted	$ 1.46	$ 0.71	$ 0.69	$ 0.59	$ 0.84	$ 1.04	$ 0.89	$ 0.73	$ 3.45	$ 3.49	$ 3.58
Weighted average shares, Basic	92,756	92,589	92,181	92,360	92,728	92,604	92,182	92,269	92,431	92,422	93,077
Weighted average shares, Diluted	93,159	92,881	92,812	93,143	93,347	93,146	92,945	93,091	92,958	93,109	93,960

Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Balance at beginning of year	$ 1,224,366	$ 1,129,301	$ 848,767
Amount charged against operating revenue	8,285,317	7,464,030	6,389,195
Accounts receivable contractual adjustments and write-offs (net of recoveries)	(8,223,648)	(7,368,965)	(6,108,661)
Balance at end of year	$ 1,286,035	$ 1,224,366	$ 1,129,301

Retirement Plans	12 Months Ended
Retirement Plans	Dec. 31, 2017
Retirement Benefits [Abstract]
Retirement Plans	15. Retirement Plans: The Company maintains six qualified contributory savings plans as allowed under Section 401(k) of the Internal Revenue Code and Section 1165(e) of the Puerto Rico Income Tax Act of 1954 (the “401(k) Plans”). The 401(k) Plans permit participant contributions and allow elective and, in certain situations, non-elective Company contributions based on each participant’s contribution or a specified percentage of eligible wages. Participants may defer a percentage of their annual compensation subject to the limits defined in the 401(k) Plans. The Company recorded expense of $50.7 million, $45.2 million and $39.7 million for the years ended December 31, 2017, 2016 and 2015, respectively, primarily related to the 401(k) Plans.

Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Expense of retirement plans related to the 401(k) Plans	$ 50.7	$ 45.2	$ 39.7