Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 07, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
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 Emerging Company	false
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		87,920,463
Entity Public Float			$ 3,943,237,534

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 36,745	$ 60,200
Restricted cash	20,000
Short-term investments	21,923	10,292
Accounts receivable, net	542,272	503,999
Prepaid expenses	18,763	15,584
Other current assets	17,706	37,160
Total current assets	657,409	627,235
Restricted cash		20,000
Investments	69,699	80,682
Property and equipment, net	133,037	123,536
Goodwill	4,382,995	4,283,963
Intangible assets, net	588,312	639,928
Other assets	103,459	91,934
Total assets	5,934,911	5,867,278
Current liabilities:
Accounts payable and accrued expenses	469,342	438,017
Current portion of long-term debt and capital lease obligations	253	1,401
Income taxes payable	30,598	92,007
Total current liabilities	500,193	531,425
Line of credit	739,500	1,110,500
Long-term debt and capital lease obligations, net	1,234,780	740,923
Long-term professional liabilities	209,060	212,274
Deferred income taxes	131,240	147,797
Other liabilities	32,254	57,905
Total liabilities	2,847,027	2,800,824
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; 87,820 and 93,721 shares issued and outstanding, respectively	878	937
Additional paid-in capital	992,647	1,017,328
Retained earnings	2,094,359	2,048,189
Total shareholders' equity	3,087,884	3,066,454
Total liabilities and shareholders' equity	$ 5,934,911	$ 5,867,278

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	87,820,000	93,721,000
Common stock, shares outstanding	87,820,000	93,721,000

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net revenue	$ 932,696	$ 896,652	$ 915,918	$ 901,857	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 3,647,123	$ 3,458,312	$ 3,183,159
Operating expenses:
Practice salaries and benefits	657,061	625,717	620,980	631,830	617,455	586,476	561,418	572,385	2,535,588	2,337,734	2,031,220
Practice supplies and other operating expenses	29,381	30,159	31,833	30,655	32,353	29,497	30,872	27,796	122,028	120,518	118,416
General and administrative expenses	112,789	102,905	107,908	108,776	108,895	101,430	103,015	103,765	432,378	417,105	372,572
Depreciation and amortization	29,891	28,709	26,518	26,163	26,414	25,116	25,735	25,614	111,281	102,879	89,264
Total operating expenses	829,122	787,490	787,239	797,424	785,117	742,519	721,040	729,560	3,201,275	2,978,236	2,611,472
Income from operations	103,574	109,162	128,679	104,433	125,703	126,432	121,904	106,037	445,848	480,076	571,687
Investment and other income	967	1,302	1,202	1,464	2,777	235	365	576	4,935	3,953	2,019
Interest expense	(25,448)	(21,782)	(21,604)	(19,935)	(19,844)	(18,428)	(18,535)	(17,752)	(88,769)	(74,559)	(63,092)
Equity in earnings of unconsolidated affiliates	2,277	1,766	1,257	1,525	(294)	(240)	689	797	6,825	952	3,185
Total non-operating expenses	(22,204)	(18,714)	(19,145)	(16,946)	(17,361)	(18,433)	(17,481)	(16,379)	(77,009)	(69,654)	(57,888)
Income before income taxes	81,370	90,448	109,534	87,487	108,342	107,999	104,423	89,658	368,839	410,422	513,799
Income tax provision	(21,156)	(24,873)	(30,122)	(24,059)	27,761	(42,119)	(40,725)	(34,967)	(100,210)	(90,050)	(189,203)
Net income	0	0	0	0					268,629	320,372	324,596
Net loss attributable to noncontrolling interests	0	0	0	0							318
Net income attributable to MEDNAX, Inc.	$ 60,214	$ 65,575	$ 79,412	$ 63,428	$ 136,103	$ 65,880	$ 63,698	$ 54,691	$ 268,629	$ 320,372	$ 324,914
Net income attributable to MEDNAX, Inc.:
Earnings per share, Basic	$ 0.69	$ 0.72	$ 0.85	$ 0.68	$ 1.47	$ 0.71	$ 0.69	$ 0.59	$ 2.95	$ 3.47	$ 3.52
Earnings per share, Diluted	$ 0.68	$ 0.72	$ 0.85	$ 0.68	$ 1.46	$ 0.71	$ 0.69	$ 0.59	$ 2.93	$ 3.45	$ 3.49
Weighted average common shares:
Basic	87,810	90,984	92,987	92,859	92,756	92,589	92,181	92,360	91,104	92,431	92,422
Diluted	88,258	91,359	93,529	93,505	93,159	92,881	92,812	93,143	91,606	92,958	93,109

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, 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)
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
Net income (loss)	268,629,000			268,629,000
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan	18,919,000	$ 5,000	18,914,000
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares		495
Issuance of restricted stock		$ 8,000	(8,000)
Issuance of restricted stock, shares		770
Stock-based compensation expense	38,703,000		38,703,000
Stock swaps	(2,661,000)	$ (1,000)	(2,660,000)
Stock swaps,shares		(56)
Forfeitures of restricted stock		$ (1,000)	1,000
Forfeitures of restricted stock, shares		(69)
Repurchased common stock	(302,160,000)	$ (70,000)	(79,631,000)	(222,459,000)
Repurchased common stock, shares		(7,041)
Excess tax benefit related to employee stock incentive plans	0
Balance at Dec. 31, 2018	$ 3,087,884,000	$ 878,000	$ 992,647,000	$ 2,094,359,000
Balance, Shares at Dec. 31, 2018		87,820

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 268,629	$ 320,372	$ 324,596
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation and amortization	111,281	102,879	89,264
Amortization of premiums, discounts and issuance costs	4,572	5,514	4,816
Stock-based compensation expense	38,703	29,573	34,000
Deferred income taxes	(24,149)	(60,073)	18,149
Other	(10,903)	(3,783)	212
Changes in assets and liabilities:
Accounts receivable	(36,598)	7,803	(34,000)
Prepaid expenses and other current assets	(5,472)	(2,792)	(783)
Other long-term assets	(395)	(2,709)	10,035
Accounts payable and accrued expenses	15,390	24,551	11,617
Income taxes payable	(61,256)	73,050	(2,234)
Payments of contingent consideration liabilities	(1,093)	(750)	(1,037)
Long-term professional liabilities	(4,490)	18,478	(3,452)
Other liabilities	(4,294)	(735)	(7,405)
Net cash provided from operating activities	289,925	511,378	443,778
Cash flows from investing activities:
Acquisition payments, net of cash acquired	(114,491)	(531,696)	(762,302)
Purchases of investments	(15,884)	(27,723)	(60,976)
Proceeds from maturities of investments	13,710	25,410	41,325
Purchases of property and equipment	(48,868)	(49,309)	(39,264)
Proceeds from sale of controlling interest in assets	22,764
Other		6,705
Net cash used in investing activities	(142,769)	(576,613)	(821,217)
Cash flows from financing activities:
Borrowings on credit agreement	1,723,500	2,846,000	1,940,000
Payments on credit agreement	(2,094,500)	(2,699,000)	(1,510,000)
Proceeds from issuance of senior notes	500,000
Payments for financing costs	(7,090)	(3,525)
Payments of contingent consideration liabilities	(5,263)	(5,449)	(10,740)
Payments on capital lease obligations	(1,356)	(2,267)	(2,130)
Excess tax benefit from exercises of stock options and vesting of restricted stock			4,241
Proceeds from issuance of common stock	16,258	23,276	22,022
Contribution from noncontrolling interests		894
Repurchases of common stock	(302,160)	(70,192)	(61,828)
Net cash (used in) provided from financing activities	(170,611)	89,737	381,565
Net (decrease) increase in cash and cash equivalents	(23,455)	24,502	4,126
Cash, cash equivalents and restricted cash at beginning of year	80,200	55,698	51,572
Cash, cash equivalents and restricted cash at end of year	56,745	80,200	55,698
Supplemental disclosure of cash flow information:
Interest	82,540	73,837	60,453
Income taxes	185,416	75,427	175,962
Non-cash investing and financing activities:
Value of common stock issued for acquisitions		2,657
Equipment financed through capital leases		684	1,619
Property and equipment included in accounts payable	$ 2,927	$ 2,700	$ 2,673

General	12 Months Ended
General	Dec. 31, 2018
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, 2018

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 party to a joint venture in which it owns a 37.5% economic interest. In January 2018, the Company entered into an additional joint venture in which it owns a 49.0% economic interest. The Company accounts for these joint ventures under the equity method of accounting because the Company exercises significant influence over, but does not control, these entities.

Recently Adopted Accounting Pronouncements

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 guidance became effective for the Company on January 1, 2018 and was adopted on a full retrospective basis. 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, 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 did not have an impact on the Company’s Consolidated Financial Statements, other than increased financial statement disclosures. The guidance requires increased disclosures, including qualitative and quantitative disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers.

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 became 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 has completed the review of its existing lease portfolio and has accumulated all of the necessary information required to properly account for leases under the new guidance. The Company has implemented a cloud-based software application, inclusive of a lease administration module and an accounting module. The Company is in the process of finalizing workflows, business processes and internal controls surrounding the new lease accounting process in order to meet the reporting and disclosure requirements.

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,
	2018			2017			2016
Neonatology and other pediatric subspecialties		36	%		37	%		39	%
Anesthesiology		35	%		38	%		39	%
Radiology		12	%		8	%		6	%
Maternal-fetal medicine		8	%		8	%		8	%
Management services		6	%		6	%		5	%
Pediatric cardiology		3	%		3	%		3	%

		100	%		100	%		100	%

Revenue Recognition

Patient service revenue is recognized at the time services are provided by the Company’s affiliated physicians. The Company’s performance obligations related to the delivery of services to patients are satisfied at the time of service. Accordingly, there are no performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period with respect to patient service revenue. Almost all of the Company’s patient service revenue is reimbursed by GHC 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 GHC Programs and third-party insurance payors for such services.

Collection of patient service revenue the Company expects to receive is normally a function of providing complete and correct billing information to the GHC Programs and third-party insurance payors within the various filing deadlines and typically occurs within 30 to 60 days of billing.

Some of the Company’s hospital agreements require hospitals to pay the Company administrative fees. Some agreements provide for fees if the hospital does not generate sufficient patient volume in order to guarantee that the Company receives a specified minimum revenue level. The Company also receives fees from hospitals for administrative services performed by its affiliated physicians providing medical director or other services at the hospital.

In addition, the Company generates revenue through its management services organization 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.

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 GHC 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 19% and 17% of net accounts receivable at December 31, 2018 and 2017, respectively.

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 in 2017.

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 five 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. Any adjustments to provisional amounts that are identified during the measurement period are 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 2018, 2017 and 2016 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, 2018 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.

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, 2018 and 2017, the Company’s money market funds had a fair value of $0.5 million and $9.2 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, 2018 and 2017, the Company’s cash surrender value of life insurance had a fair value of $10.5 million and $15.6 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, 2018 and 2017, the Company’s contingent consideration liabilities had a fair value of $20.0 million and $30.5 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 was measured at fair value, it 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”) and 6.25% senior unsecured notes due 2027 (the “2027 Notes”).

Investments

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Investments

3. Investments:

Investments held are summarized as follows (in thousands):


	December 31, 2018				December 31, 2017
	Short-Term		Long-Term		Short-Term		Long-Term
Municipal debt securities	$	18,473	$	30,841	$	8,312	$	46,195
Federal home loan securities		2,000		34,393		1,000		30,322
Certificates of deposit		1,450		4,465		980		4,165

	$	21,923	$	69,699	$	10,292	$	80,682

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


	December 31,
	2018		2017
Due after one year through five years	$	69,699	$	78,561
Due after five years through six years		—		2,121

	$	69,699	$	80,682

Accounts Receivable and Net Revenue

12 Months Ended

Dec. 31, 2018

Text Block [Abstract]

Accounts Receivable and Net Revenue

4. Accounts Receivable and Net Revenue:

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


	December 31,
	2018			2017
Gross accounts receivable	$	2,031,341		$	1,790,034
Allowance for contractual adjustments and uncollectibles		(1,489,069	)		(1,286,035	)

	$	542,272		$	503,999

Net revenue consists of the following (in thousands):


	Years Ended December 31,
	2018		2017		2016
Net patient service revenue	$	3,067,784	$	2,915,648	$	2,760,192
Hospital contract administrative fees		363,369		315,778		271,886
Management services and other		215,970		226,886		151,081

	$	3,647,123	$	3,458,312	$	3,183,159

The following is a summary of our payor mix, expressed as a percentage of net revenue, exclusive of administrative fees and revenue related to management services and other, for the periods indicated:


	Years Ended December 31,
	2018			2017			2016
Contracted managed care		70	%		70	%		70	%
Government		24	%		25	%		23	%
Other third-parties		4	%		4	%		6	%
Private-pay patients		2	%		1	%		1	%

		100	%		100	%		100	%

Accounts receivable of $542.3 million and $504.0 million at December 31, 2018 and 2017, respectively, consist primarily of amounts due from GHC Programs and third-party insurance payors for services provided by the Company’s affiliated physicians.

Net revenue of $3.6 billion, $3.5 billion and $3.2 billion for the years ended December 31, 2018, 2017 and 2016, 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 GHC Programs, shifts in the percentage of patient services being reimbursed under GHC 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 GHC 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.

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property and Equipment

5. Property and Equipment:

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


	December 31,
	2018			2017
Building	$	33,189		$	33,024
Land		6,683			6,683
Equipment and other		300,981			253,453

		340,853			293,160
Accumulated depreciation		(207,816	)		(169,624	)

	$	133,037		$	123,536

At December 31, 2018 and 2017, property and equipment includes medical and other equipment held under capital leases of $4.8 million and $6.1 million, and related accumulated depreciation of $4.0 million and $4.6 million, respectively. The Company recorded depreciation expense of $38.5 million, $33.9 million and $29.0 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Business Acquisitions	12 Months Ended
Business Acquisitions	Dec. 31, 2018
Business Combinations [Abstract]
Business Acquisitions	6. Business Acquisitions: During the year ended December 31, 2018, the Company completed nine physician group practice acquisitions, including five radiology practices, two neonatology practices and two other pediatric subspecialty practices. The acquisition-date fair value of the total consideration for the nine acquisitions was $111.8 million, net of cash acquired. In connection with these acquisitions, the Company recorded goodwill of $95.0 million, other intangible assets consisting primarily of physician and hospital agreements of $17.2 million, current assets of $1.7 million and other liabilities of $2.1 million. 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 practice management support and a technology platform enabling radiology to be practiced at a national level, as well as teleradiology capabilities that can enhance a physician group’s efficiency, provide subspecialty access and help them to grow strategically and remain competitive while meeting the demands of their hospital partners, third-party 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. During the year ended December 31, 2018, in connection with certain prior-period acquisitions, the Company paid $6.4 million for contingent consideration and $1.2 million for purchase consideration that had been held back pending satisfaction of certain conditions. Of these amounts, all except for the accretion recorded during 2018 were accrued as of December 31, 2017. In addition, the Company recorded a decrease of $5.3 million related to the change in the fair value of a contingent consideration agreement for which the probability of the achievement of certain performance measures was updated. This change in fair value of contingent consideration was recorded within operating expenses. In connection with certain prior-period acquisitions, the Company also recorded a net increase in goodwill of $4.0 million composed of a decrease in current assets of $1.2 million, a decrease in noncurrent assets of $1.5 million and a decrease in liabilities of $0.2 million for measurement-period adjustments resulting from the finalization of acquisition accounting as well as additional cash consideration of $1.5 million related to a working capital true up. In January 2018, the Company completed the sale of a controlling interest and the contribution of remaining assets to a joint venture related to the $46.0 million of assets held for sale at December 31, 2017. The Company accounts for its 49.0% economic interest in the joint venture as an equity method investment. The investment in this joint venture is included in other assets as presented in the Company’s Condensed Consolidated Balance Sheet. On November 1, 2018, the Company announced the initiation of a process to potentially divest the Company’s management services service line to allow the Company to focus the organization on its core physician services business. There can be no assurance that this process will result in a transaction, and the Company may decide to retain all or part of the management services service line. The Company had expected that the management services service line could be classified as assets and liabilities held for sale within the Company’s Consolidated Balance Sheets and that historical operating results of the service line could be reported as discontinued operations in the Company’s Consolidated Statements of Income for the year ended December 31, 2018; however, the criteria for such classification was not met at December 31, 2018. The management services service line continues to be classified as held and used as of December 31, 2018. 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. 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, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

7. Goodwill and Intangible Assets:

Goodwill was $4.4 billion and $4.3 billion at December 31, 2018 and 2017, respectively. The change in the carrying amount of goodwill of $99.0 million during the year ended December 31, 2018 is primarily related to the Company’s 2018 acquisitions. The Company expects that $63.0 million of the goodwill recorded during the year ended December 31, 2018 will be deductible for tax purposes.

The Company’s management services reporting unit has experienced lower operating results than previously forecasted primarily due to a slower rate of new customer bookings and an increase in customer termination activity. The Company continues to believe that the fair value of the reporting unit exceeds the carrying value, and accordingly the goodwill assigned to the management services reporting unit is not impaired. Although the Company believes that the current assumptions and estimates used in its goodwill analysis are reasonable, supportable and appropriate, continued efforts to maintain or improve the performance of this business could be impacted by unfavorable or unforeseen changes which could impact the existing assumptions used in the impairment analysis. Various factors could reasonably be expected to unfavorably impact existing assumptions, primarily delays in new customer bookings and the related delay in revenue from new customers, increases in customer termination activity or increases in operating costs. Accordingly, there can be no assurance that the estimates and assumptions made for the purposes of the goodwill impairment analysis will prove to be accurate predictions of future performance. The carrying value of the Company’s management services reporting unit included goodwill of $321.6 million as of December 31, 2018. The Company will continue to closely monitor the performance of the management services reporting unit. If an impairment loss is required in a future period, it could have a material adverse effect on the Company’s business, financial condition, results of operations, cash flows and the trading price of the Company’s securities.

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


	December 31, 2018
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Physician and hospital agreements	$	376,871	$	(223,589)		$	153,282
Customer relationships		443,300		(71,870	)		371,430
Trade names		43,156		(4,630	)		38,526
Patented and other technology		47,561		(22,487	)		25,074

	$	910,888	$	(322,576)		$	588,312


	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

During the year ended December 31, 2018, the Company recorded intangible assets related to acquisitions totaling $17.2 million, consisting primarily of physician and hospital agreements. The weighted-average amortization period for these physician and hospital agreements is approximately nine years.

Amortization expense for intangible assets was $72.8 million, $68.9 million and $60.3 million for the years ended December 31, 2018, 2017 and 2016, respectively.

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


2019	$	66,532
2020		59,969
2021		53,771
2022		46,249
2023		40,448

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2018

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,
	2018		2017
Accounts payable	$	31,059	$	34,632
Accrued salaries and bonuses		249,834		225,429
Accrued payroll taxes and benefits		80,369		75,672
Accrued professional liabilities		34,931		37,912
Accrued contingent consideration		18,760		6,259
Accrued interest		9,477		4,495
Other accrued expenses		44,912		53,618

	$	469,342	$	438,017

Accrued Professional Liabilities

12 Months Ended

Dec. 31, 2018

Health Care Organizations [Abstract]

Accrued Professional Liabilities

9. Accrued Professional Liabilities:

At December 31, 2018 and 2017, the Company’s total accrued professional liabilities of $244.0 million and $250.2 million, respectively, included incurred but not reported loss reserves of $139.1 million and $138.5 million, respectively, and loss reserves for reported claims of $104.9 million and $111.7 million, respectively. Of the total liability, $34.9 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 $16.7 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, 2018, 2017 and 2016 is as follows (in thousands):


	Years Ended December 31,
	2018			2017			2016
Balance at beginning of year	$	250,187		$	202,052		$	202,527
Assumed liabilities through acquisition		1,276			20,716			—
Provision (adjustment) for losses related to:
Current year		34,483			41,291			38,129
Prior years		10,299			9,983			(25,428	)

Total provision for losses		44,782			51,274			12,701
Claim payments related to:
Current year		(555	)		(712	)		(766	)
Prior years		(51,699	)		(23,143	)		(12,410	)

Total payments		(52,254	)		(23,855	)		(13,176	)

Balance at end of year	$	243,991		$	250,187		$	202,052

The net decrease in the Company’s total accrued professional liability for the year ended December 31, 2018 was primarily related to an increase in claims payments made in the current year, partially offset by overall unfavorable trends in the Company’s claims experience that impacted its provision for losses. The net increase in the Company’s total accrued professional liability for the year ended December 31, 2017 was primarily related to overall unfavorable trends in the Company’s claims experience that impacted its provision for losses and growth in the program from acquisitions.

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

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

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

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

The Company’s 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. In November 2018, the Company amended and restated its Credit Agreement to make certain technical, conforming and other changes. The 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 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 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 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 Credit Agreement, notwithstanding the ability of the Company to meet its debt service obligations. The 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 Credit Agreement.

In December 2015, the Company completed a private offering of $750.0 million aggregate principal amount of 2023 Notes. In November 2018, the Company completed a private offering of $500.0 million aggregate principal amount of 2027 Notes. The Company’s obligations under the 2023 Notes and the 2027 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 Notes accrues at the rate of 5.25% per annum and is payable semi-annually in arrears on June 1 and December 1. Interest on the 2027 Notes accrues at the rate of 6.25% per annum and is payable semi-annually in arrears on January 15 and July 15, with the initial interest payment due on January 15, 2019.

As of December 31, 2018, the Company may redeem all or a portion of the 2023 Notes, at the redemption prices of 102.625% in 2019, 101.313% in 2020 and 100% in 2021 and thereafter, plus accrued and unpaid interest to the redemption date.

At any time prior to January 15, 2022, the Company may redeem all or a portion of the 2027 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 January 15, 2022, the Company may redeem up to 35% of the aggregate principal amount of the 2027 Notes at a redemption price of 106.250% 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 January 15, 2022, the Company may redeem all or a portion of the 2027 Notes, at the redemption prices of 104.688% in 2022, 103.125% in 2023, 101.563% in 2024 and 100% in 2025 and thereafter, plus accrued and unpaid interest to the redemption date.

The indenture under which the 2023 Notes and the 2027 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 Notes or the 2027 Notes, upon the occurrence of a change in control of MEDNAX, we may be required to repurchase the 2023 Notes or the 2027 Notes at a purchase price equal to 101% of the aggregate principal amount of the 2023 Notes and the 2027 Notes repurchased plus accrued and unpaid interest.

The carrying value of the Company’s long-term debt was $2.0 billion and $1.8 billion at December 31, 2018 and 2017, respectively, and consisted of the following (in thousands):


	December 31, 2018
	Principal		Unamortized Debt Issuance Costs			Total
Senior Notes	$	1,250,000	$	(15,408	)	$	1,234,592
Revolving line of credit		739,500		(4,274	)		735,226

Total	$	1,989,500	$	(19,682	)	$	1,969,818


	December 31, 2017
	Principal		Unamortized Debt Issuance Costs			Total
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

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 Company has outstanding letters of credit which reduced the amount available under the Credit Agreement by $0.2 million at December 31, 2018. At December 31, 2018, the Company had an available balance on its Credit Agreement of $1.3 billion.

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 and 2027 Notes were estimated using trading prices as of December 31, 2018 and 2017, respectively, as Level 2 inputs to estimate fair value and are summarized as follows (in thousands):


	December 31,
	2018		2017
2023 Notes	$	736,725	$	763,125
2027 Notes		482,500		—

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


	December 31,
	2018			2017
Capital lease obligations	$	441		$	1,826
Less: Current portion		(253	)		(1,401	)

Long-term portion	$	188		$	425

The amounts due under the terms of the Company’s capital lease obligations at December 31, 2018 are as follows:


2019	$	253
2020		114
2021		74

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes:

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


	December 31,
	2018			2017			2016
Federal:
Current	$	97,754		$	130,053		$	166,758
Deferred		(20,176	)		(63,038	)		15,596

		77,578			67,015			182,354

State:
Current		26,605			20,070			4,296
Deferred		(3,973	)		2,965			2,553

		22,632			23,035			6,849

Total	$	100,210		$	90,050		$	189,203

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

Beginning on January 1, 2018, the Company’s statutory tax rate was reduced from 35.0% to 21.0% as a result of legislation enacted under the Tax Cuts and Jobs Act of 2017 (“TCJA”). The effective tax rate was 27.2%, 21.9% and 36.8% for the years ended December 31, 2018, 2017 and 2016, 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 under the TCJA. 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.

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


	December 31,
	2018			2017			2016
Tax at statutory rate		21.00	%		35.00	%		35.00	%
State income tax, net of federal benefit		4.80			3.33			2.94
Non-deductible expenses		0.44			0.49			0.43
Change in accrual estimates relating to uncertain tax positions		0.05			0.02			(2.11	)
Change in valuation allowance		—			—			0.48
Other, net		1.20			0.16			0.06
Change in tax law		(0.32	)		(17.06	)		—

Income tax provision		27.17	%		21.94	%		36.80	%

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,
	2018			2017
Allowance for uncollectible accounts	$	194,876		$	80,056
Reserves and accruals		59,270			45,454
Stock-based compensation		9,201			7,975
Net operating loss carryforward		25,226			28,569
Property and equipment		26			685
Other		1,197			970

Deferred tax assets before valuation allowance		289,796			163,709
Less: Valuation allowance		(2,628	)		(2,615	)

Deferred tax assets, net of valuation allowance		287,168			161,094

Gross deferred tax liabilities:
Amortization		(286,552	)		(258,618	)

Accounting method changes		(109,418	)		(4,150	)
Accrual to cash adjustment		(39	)		(31,290	)
Other		(489	)		—

Total deferred tax liabilities		(396,498	)		(294,058	)

Net deferred tax liability	$	(109,330	)	$	(132,964	)

The Company’s net deferred tax liability decreased by $23.6 million during 2018. During 2018, certain of the Company’s affiliated professional contractors elected to change their method of accounting from cash basis to accrual basis for income tax purposes. During the year ended December 31, 2018, the increases in allowance for uncollectible accounts of $114.8 million and accounting method changes of $105.3 million as well as the decrease in accrual to cash adjustment of $31.3 million primarily relate to these accounting method changes.

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 years ended December 31, 2018 and 2017, income tax expense of $1.4 million and $0.2 million, respectively, was recognized for excess tax deficiencies. For the year ended December 31, 2016, additional paid-in-capital was increased by $4.2 million for excess tax benefits.

The Company has net operating loss carryforwards for federal and state tax purposes totaling $101.9 million, $116.0 million and $130.0 million at December 31, 2018, 2017 and 2016, respectively. With respect to the December 31, 2018 balance, approximately $74.3 million expires at various times from 2019 through 2038, and $27.6 million does not expire.

As of December 31, 2018, 2017 and 2016, the Company’s liability for uncertain tax positions, excluding accrued interest and penalties, was $11.2 million, $11.0 million and $9.5 million, respectively. As of December 31, 2018, the Company had $10.9 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, 2018, 2017 and 2016 (in thousands):


	Years Ended December 31,
	2018			2017			2016
Balance at beginning of year	$	10,972		$	9,469		$	18,447
Increases related to prior year tax positions		385			2,284			301
Decreases related to prior year tax positions		—			(143	)		(3,927	)
Increases related to current year tax positions		2,900			1,430			2,258
Settlements		—			—			(5,644	)
Decreases related to lapse of statutes of limitation		(3,072	)		(2,068	)		(1,966	)

Balance at end of year	$	11,185		$	10,972		$	9,469

During the years ended December 31, 2018 and 2017, the Company increased its liability for uncertain tax positions by a total of $0.2 million and $1.5 million, respectively, primarily related to additional taxes on current and prior year positions, partially offset by the expiration of statutes of limitation. In addition, the Company anticipates that its liability for uncertain tax positions will increase by $0.2 million over the next 12 months.

The Company includes interest and penalties related to income tax liabilities in income tax expense. The income tax benefit recognized by the Company for interest and penalties during the year ended December 31, 2018 was nominal. The Company recognized income tax benefits of $0.2 million and $7.9 million related to interest and penalties during the years ended December 31, 2017 and 2016, respectively. At December 31, 2018 and 2017, the Company’s accrued liability for interest and penalties related to income tax liabilities totaled $1.1 million and $1.2 million, respectively.

The Company is currently subject to U.S. Federal and various state income tax examinations for the tax years 2014 through 2017.

Common and Common Equivalent Shares

12 Months Ended

Dec. 31, 2018

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, 2018, 2017 and 2016 is as follows (in thousands):


	Years Ended December 31,
	2018		2017		2016
Weighted average number of common shares outstanding		91,104		92,431		92,422
Weighted average number of dilutive common share equivalents		502		527		687

Weighted average number of common and common equivalent shares outstanding		91,606		92,958		93,109

Antidilutive securities not included in the diluted net income per common share calculation		214		107		2

Stock Incentive Plans and Stock Purchase Plans

12 Months Ended

Dec. 31, 2018

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, 2018, the Company had 2.0 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.

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, 2018, 0.4 million shares were issued under the ESPP and SPP. At December 31, 2018, the Company had 1.6 million shares in aggregate reserved for issuance under the ESPP and SPP.

The Company recognized $38.7 million, $29.6 million and $34.0 million of stock-based compensation expense related to its stock incentive plans, the ESPP and the SPP during the years ended December 31, 2018, 2017 and 2016, 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, 2018 are as follows:


	Number of Shares			Weighted Average Fair Value
Non-vested shares at January 1, 2018		1,041,034		$	60.21
Awarded		770,480		$	51.99
Forfeited		(69,293	)	$	56.65
Vested		(431,368	)	$	63.57

Non-vested shares at December 31, 2018		1,310,853		$	54.46

The aggregate fair value of the restricted and deferred stock that vested during the years ended December 31, 2018, 2017 and 2016 was $27.4 million, $29.3 million and $29.8 million, respectively.

The weighted average grant-date fair value of restricted and deferred stock awards that were granted during the years ended December 31, 2018, 2017 and 2016 was $51.99, $54.22 and $67.90, respectively.

At December 31, 2018, 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 1.4 years was $30.8 million.

The Company did not grant any stock options in 2018, 2017, or 2016, 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, 2018 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, 2018		246,342		$	27.51
Exercised		(133,366	)	$	27.38			$	2.8

Outstanding and exercisable at December 31, 2018		112,976		$	27.65		1.3	$	0.7

The aggregate intrinsic value of stock options exercised during the years ended December 31, 2018, 2017 and 2016 was $2.8 million, $5.5 million and $6.8 million, respectively.

There were no excess tax benefits recognized in additional paid-in capital in 2018 or 2017 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 year ended December 31, 2016 was $4.1 million. The cash proceeds received from the exercise of stock options for the years ended December 31, 2018, 2017 and 2016 were $3.7 million, $4.8 million and $4.7 million, respectively.

Common Stock Repurchase Programs	12 Months Ended
Common Stock Repurchase Programs	Dec. 31, 2018
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. Shares repurchased by the Company during the second quarter of 2018 completed the repurchases under the program with respect to issuances of shares under the Company’s equity compensation programs during 2018. In August 2018, the Company announced that its Board of Directors had authorized the repurchase of up to $500.0 million of the Company’s common stock in addition to its existing share repurchase program. As part of this repurchase program, on August 31, 2018, the Company entered into an uncollared accelerated share repurchase (“ASR”) agreement with an investment bank. Under the ASR agreement, the Company agreed to purchase $250.0 million of its common stock in total. On September 4, 2018, the Company paid a total of $250.0 million to the investment bank, which in turn delivered to the Company approximately 4.2 million shares of the Company’s common stock in total based on the market price of a share of Company common stock on August 31, 2018. The payment was recorded as a reduction to the respective components of shareholders’ equity. The ASR agreement was funded by borrowings under the Company’s Credit Agreement discussed in Note 10. Final settlement of the ASR occurred in December 2018 with the delivery to the Company of approximately 1.7 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. Under the share repurchase programs described above, the Company repurchased approximately 7.0 million shares of its common stock for approximately $302.2 million during the year ended December 31, 2018, inclusive of 54,909 shares withheld to satisfy minimum statutory withholding obligations of $2.5 million in connection with the vesting of restricted stock and exercises of stock options during the second quarter of 2018. 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. 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, 2018

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 securities. The Company has not included an accrual for these matters as of December 31, 2018 in its Condensed 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, 2018, 2017 and 2016 was $42.9 million, $42.6 million and $38.0 million, respectively.

Future minimum lease payments under non-cancelable operating leases as of December 31, 2018 are as follows (in thousands):


2019	$	30,824
2020		22,038
2021		17,946
2022		12,708
2023		9,440
Thereafter		10,522

	$	103,478

Selected Quarterly Financial Information

12 Months Ended

Dec. 31, 2018

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, 2018 and 2017 (in thousands, except for per share data):


	2018 Quarters
	First			Second			Third			Fourth
Net revenue	$	901,857		$	915,918		$	896,652		$	932,696

Operating expenses:
Practice salaries and benefits		631,830			620,980			625,717			657,061
Practice supplies and other operating expenses		30,655			31,833			30,159			29,381
General and administrative expenses		108,776			107,908			102,905			112,789
Depreciation and amortization		26,163			26,518			28,709			29,891

Total operating expenses		797,424			787,239			787,490			829,122

Income from operations		104,433			128,679			109,162			103,574
Investment and other income		1,464			1,202			1,302			967
Interest expense		(19,935	)		(21,604	)		(21,782	)		(25,448	)
Equity in earnings of unconsolidated affiliates		1,525			1,257			1,766			2,277

Total non-operating expenses		(16,946	)		(19,145	)		(18,714	)		(22,204	)
Income before income taxes		87,487			109,534			90,448			81,370
Income tax provision		(24,059	)		(30,122	)		(24,873	)		(21,156	)

Net income	$	63,428		$	79,412		$	65,575		$	60,214

Per common and common equivalent share data (1):
Net income:
Basic	$	0.68		$	0.85		$	0.72		$	0.69

Diluted	$	0.68		$	0.85		$	0.72		$	0.68

Weighted average common shares:
Basic		92,859			92,987			90,984			87,810

Diluted		93,505			93,529			91,359			88,258

(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.


	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 (loss) 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	$	54,691		$	63,698		$	65,880		$	136,103

Per common and common equivalent share data (2):
Net income:
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

(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 (Policies)

12 Months Ended

Dec. 31, 2018

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,
	2018			2017			2016
Neonatology and other pediatric subspecialties		36	%		37	%		39	%
Anesthesiology		35	%		38	%		39	%
Radiology		12	%		8	%		6	%
Maternal-fetal medicine		8	%		8	%		8	%
Management services		6	%		6	%		5	%
Pediatric cardiology		3	%		3	%		3	%

		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

Restricted cash consists of funds in escrow related to a potential future payment for contingent consideration for an acquisition completed in 2017.

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, 2018

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,
	2018			2017			2016
Neonatology and other pediatric subspecialties		36	%		37	%		39	%
Anesthesiology		35	%		38	%		39	%
Radiology		12	%		8	%		6	%
Maternal-fetal medicine		8	%		8	%		8	%
Management services		6	%		6	%		5	%
Pediatric cardiology		3	%		3	%		3	%

		100	%		100	%		100	%

Investments (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

Investments held are summarized as follows (in thousands):


	December 31, 2018				December 31, 2017
	Short-Term		Long-Term		Short-Term		Long-Term
Municipal debt securities	$	18,473	$	30,841	$	8,312	$	46,195
Federal home loan securities		2,000		34,393		1,000		30,322
Certificates of deposit		1,450		4,465		980		4,165

	$	21,923	$	69,699	$	10,292	$	80,682

Schedule of Contractual Maturities of Long-Term Investments

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


	December 31,
	2018		2017
Due after one year through five years	$	69,699	$	78,561
Due after five years through six years		—		2,121

	$	69,699	$	80,682

Accounts Receivable and Net Revenue (Tables)

12 Months Ended

Dec. 31, 2018

Text Block [Abstract]

Schedule of Accounts Receivable, Net

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


	December 31,
	2018			2017
Gross accounts receivable	$	2,031,341		$	1,790,034
Allowance for contractual adjustments and uncollectibles		(1,489,069	)		(1,286,035	)

	$	542,272		$	503,999

Schedule of Net Revenue

Net revenue consists of the following (in thousands):


	Years Ended December 31,
	2018		2017		2016
Net patient service revenue	$	3,067,784	$	2,915,648	$	2,760,192
Hospital contract administrative fees		363,369		315,778		271,886
Management services and other		215,970		226,886		151,081

	$	3,647,123	$	3,458,312	$	3,183,159

Schedule of Percentage of Net Revenue


	Years Ended December 31,
	2018			2017			2016
Contracted managed care		70	%		70	%		70	%
Government		24	%		25	%		23	%
Other third-parties		4	%		4	%		6	%
Private-pay patients		2	%		1	%		1	%

		100	%		100	%		100	%

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

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


	December 31,
	2018			2017
Building	$	33,189		$	33,024
Land		6,683			6,683
Equipment and other		300,981			253,453

		340,853			293,160
Accumulated depreciation		(207,816	)		(169,624	)

	$	133,037		$	123,536

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Intangible Assets, Net

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


	December 31, 2018
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Physician and hospital agreements	$	376,871	$	(223,589)		$	153,282
Customer relationships		443,300		(71,870	)		371,430
Trade names		43,156		(4,630	)		38,526
Patented and other technology		47,561		(22,487	)		25,074

	$	910,888	$	(322,576)		$	588,312


	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

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):


2019	$	66,532
2020		59,969
2021		53,771
2022		46,249
2023		40,448

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Expenses

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


	December 31,
	2018		2017
Accounts payable	$	31,059	$	34,632
Accrued salaries and bonuses		249,834		225,429
Accrued payroll taxes and benefits		80,369		75,672
Accrued professional liabilities		34,931		37,912
Accrued contingent consideration		18,760		6,259
Accrued interest		9,477		4,495
Other accrued expenses		44,912		53,618

	$	469,342	$	438,017

Accrued Professional Liabilities (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018, 2017 and 2016 is as follows (in thousands):


	Years Ended December 31,
	2018			2017			2016
Balance at beginning of year	$	250,187		$	202,052		$	202,527
Assumed liabilities through acquisition		1,276			20,716			—
Provision (adjustment) for losses related to:
Current year		34,483			41,291			38,129
Prior years		10,299			9,983			(25,428	)

Total provision for losses		44,782			51,274			12,701
Claim payments related to:
Current year		(555	)		(712	)		(766	)
Prior years		(51,699	)		(23,143	)		(12,410	)

Total payments		(52,254	)		(23,855	)		(13,176	)

Balance at end of year	$	243,991		$	250,187		$	202,052

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

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Long-Term Debt

The carrying value of the Company’s long-term debt was $2.0 billion and $1.8 billion at December 31, 2018 and 2017, respectively, and consisted of the following (in thousands):


	December 31, 2018
	Principal		Unamortized Debt Issuance Costs			Total
Senior Notes	$	1,250,000	$	(15,408	)	$	1,234,592
Revolving line of credit		739,500		(4,274	)		735,226

Total	$	1,989,500	$	(19,682	)	$	1,969,818


	December 31, 2017
	Principal		Unamortized Debt Issuance Costs			Total
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

Summary of Estimated Fair Value of Notes

The estimated fair value of the Company’s 2023 Notes and 2027 Notes were estimated using trading prices as of December 31, 2018 and 2017, respectively, as Level 2 inputs to estimate fair value and are summarized as follows (in thousands):


	December 31,
	2018		2017
2023 Notes	$	736,725	$	763,125
2027 Notes		482,500		—

Schedule of Capital Lease Obligations

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


	December 31,
	2018			2017
Capital lease obligations	$	441		$	1,826
Less: Current portion		(253	)		(1,401	)

Long-term portion	$	188		$	425

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, 2018 are as follows:


2019	$	253
2020		114
2021		74

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

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,
	2018			2017			2016
Federal:
Current	$	97,754		$	130,053		$	166,758
Deferred		(20,176	)		(63,038	)		15,596

		77,578			67,015			182,354

State:
Current		26,605			20,070			4,296
Deferred		(3,973	)		2,965			2,553

		22,632			23,035			6,849

Total	$	100,210		$	90,050		$	189,203

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,
	2018			2017			2016
Tax at statutory rate		21.00	%		35.00	%		35.00	%
State income tax, net of federal benefit		4.80			3.33			2.94
Non-deductible expenses		0.44			0.49			0.43
Change in accrual estimates relating to uncertain tax positions		0.05			0.02			(2.11	)
Change in valuation allowance		—			—			0.48
Other, net		1.20			0.16			0.06
Change in tax law		(0.32	)		(17.06	)		—

Income tax provision		27.17	%		21.94	%		36.80	%

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,
	2018			2017
Allowance for uncollectible accounts	$	194,876		$	80,056
Reserves and accruals		59,270			45,454
Stock-based compensation		9,201			7,975
Net operating loss carryforward		25,226			28,569
Property and equipment		26			685
Other		1,197			970

Deferred tax assets before valuation allowance		289,796			163,709
Less: Valuation allowance		(2,628	)		(2,615	)

Deferred tax assets, net of valuation allowance		287,168			161,094

Gross deferred tax liabilities:
Amortization		(286,552	)		(258,618	)

Accounting method changes		(109,418	)		(4,150	)
Accrual to cash adjustment		(39	)		(31,290	)
Other		(489	)		—

Total deferred tax liabilities		(396,498	)		(294,058	)

Net deferred tax liability	$	(109,330	)	$	(132,964	)

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, 2018, 2017 and 2016 (in thousands):


	Years Ended December 31,
	2018			2017			2016
Balance at beginning of year	$	10,972		$	9,469		$	18,447
Increases related to prior year tax positions		385			2,284			301
Decreases related to prior year tax positions		—			(143	)		(3,927	)
Increases related to current year tax positions		2,900			1,430			2,258
Settlements		—			—			(5,644	)
Decreases related to lapse of statutes of limitation		(3,072	)		(2,068	)		(1,966	)

Balance at end of year	$	11,185		$	10,972		$	9,469

Common and Common Equivalent Shares (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018, 2017 and 2016 is as follows (in thousands):


	Years Ended December 31,
	2018		2017		2016
Weighted average number of common shares outstanding		91,104		92,431		92,422
Weighted average number of dilutive common share equivalents		502		527		687

Weighted average number of common and common equivalent shares outstanding		91,606		92,958		93,109

Antidilutive securities not included in the diluted net income per common share calculation		214		107		2

Stock Incentive Plans and Stock Purchase Plans (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018 are as follows:


	Number of Shares			Weighted Average Fair Value
Non-vested shares at January 1, 2018		1,041,034		$	60.21
Awarded		770,480		$	51.99
Forfeited		(69,293	)	$	56.65
Vested		(431,368	)	$	63.57

Non-vested shares at December 31, 2018		1,310,853		$	54.46

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, 2018 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, 2018		246,342		$	27.51
Exercised		(133,366	)	$	27.38			$	2.8

Outstanding and exercisable at December 31, 2018		112,976		$	27.65		1.3	$	0.7

Selected Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Summary of Company's Selected Quarterly Financial Information


	2018 Quarters
	First			Second			Third			Fourth
Net revenue	$	901,857		$	915,918		$	896,652		$	932,696

Operating expenses:
Practice salaries and benefits		631,830			620,980			625,717			657,061
Practice supplies and other operating expenses		30,655			31,833			30,159			29,381
General and administrative expenses		108,776			107,908			102,905			112,789
Depreciation and amortization		26,163			26,518			28,709			29,891

Total operating expenses		797,424			787,239			787,490			829,122

Income from operations		104,433			128,679			109,162			103,574
Investment and other income		1,464			1,202			1,302			967
Interest expense		(19,935	)		(21,604	)		(21,782	)		(25,448	)
Equity in earnings of unconsolidated affiliates		1,525			1,257			1,766			2,277

Total non-operating expenses		(16,946	)		(19,145	)		(18,714	)		(22,204	)
Income before income taxes		87,487			109,534			90,448			81,370
Income tax provision		(24,059	)		(30,122	)		(24,873	)		(21,156	)

Net income	$	63,428		$	79,412		$	65,575		$	60,214

Per common and common equivalent share data (1):
Net income:
Basic	$	0.68		$	0.85		$	0.72		$	0.69

Diluted	$	0.68		$	0.85		$	0.72		$	0.68

Weighted average common shares:
Basic		92,859			92,987			90,984			87,810

Diluted		93,505			93,529			91,359			88,258

(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.


	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 (loss) 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	$	54,691		$	63,698		$	65,880		$	136,103

Per common and common equivalent share data (2):
Net income:
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

(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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Nov. 30, 2018	Jan. 31, 2018	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Equity method ownership percentage in joint venture	49.00%
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	$ 0.5	$ 9.2
Cash surrender fair value of life insurance	10.5	15.6
Contingent consideration liabilities related to acquisitions	$ 20.0	$ 30.5
5.25% Senior Unsecured Notes Due 2023 [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument interest rate	5.25%				5.25%
6.25% Senior Unsecured Notes Due 2027 [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument interest rate	6.25%		6.25%
Unnamed Corporate Joint Venture [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method ownership percentage in joint venture	37.50%			49.00%
Government Contracts Concentration Risk [Member] \| Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of net accounts receivable	19.00%	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	5 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, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net revenue in percentage	100.00%	100.00%	100.00%
Neonatology and Other Pediatric Subspecialties [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	36.00%	37.00%	39.00%
Anesthesiology [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	35.00%	38.00%	39.00%
Radiology And Teleradiology [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	12.00%	8.00%	6.00%
Maternal-Fetal Medicine [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	8.00%	8.00%	8.00%
Management Services [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	6.00%	6.00%	5.00%
Pediatric Cardiology [Member]
Segment Reporting Information [Line Items]
Net revenue in percentage	3.00%	3.00%	3.00%

Investments - Schedule of Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	$ 21,923	$ 10,292
Long-Term	69,699	80,682
Municipal Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	18,473	8,312
Long-Term	30,841	46,195
Federal Home Loan Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	2,000	1,000
Long-Term	34,393	30,322
Certificates of Deposit [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	1,450	980
Long-Term	$ 4,465	$ 4,165

Investments - Schedule of Contractual Maturities of Long-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Due after one year through five years	$ 69,699	$ 78,561
Due after five years through six years		2,121
Total	$ 69,699	$ 80,682

Accounts Receivable and Net Revenue - Schedule of Accounts Receivable, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Gross accounts receivable	$ 2,031,341	$ 1,790,034
Allowance for contractual adjustments and uncollectibles	(1,489,069)	(1,286,035)
Accounts receivable, net	$ 542,272	$ 503,999

Accounts Receivable and Net Revenue - Schedule of Net Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Abstract]
Net revenue	$ 932,696	$ 896,652	$ 915,918	$ 901,857	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 3,647,123	$ 3,458,312	$ 3,183,159
Net patient service revenue
Disaggregation of Revenue [Abstract]
Net revenue									3,067,784	2,915,648	2,760,192
Hospital contract administrative fees
Disaggregation of Revenue [Abstract]
Net revenue									363,369	315,778	271,886
Management Services [Member]
Disaggregation of Revenue [Abstract]
Net revenue									$ 215,970	$ 226,886	$ 151,081

Accounts Receivable and Net Revenue - Schedule of Net Patient Service Revenue by Type of Payor (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Percentage of net patient service revenue	100.00%	100.00%	100.00%
Contracted Managed Care [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Percentage of net patient service revenue	70.00%	70.00%	70.00%
Government [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Percentage of net patient service revenue	24.00%	25.00%	23.00%
Other Third-Parties [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Percentage of net patient service revenue	4.00%	4.00%	6.00%
Private-Pay Patients [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Percentage of net patient service revenue	2.00%	1.00%	1.00%

Accounts Receivable and Net Revenue - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Accounts receivable, net	$ 542,272				$ 503,999				$ 542,272	$ 503,999
Net revenue	$ 932,696	$ 896,652	$ 915,918	$ 901,857	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 3,647,123	$ 3,458,312	$ 3,183,159

Property Plant and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Building	$ 33,189	$ 33,024
Land	6,683	6,683
Equipment and other	300,981	253,453
Property and equipment, gross	340,853	293,160
Accumulated depreciation	(207,816)	(169,624)
Property and equipment, net	$ 133,037	$ 123,536

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Medical and other equipment held under capital leases	$ 340,853	$ 293,160
Accumulated depreciation of property and equipment held under capital leases	207,816	169,624
Recorded depreciation expense	38,500	33,900	$ 29,000
Medical and Other Equipment Held under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Medical and other equipment held under capital leases	4,800	6,100
Accumulated depreciation of property and equipment held under capital leases	$ 4,000	$ 4,600

Business Acquisitions - Additional Information (Detail) $ in Millions		12 Months Ended
	Mar. 31, 2017	Dec. 31, 2018 USD ($) Company	Dec. 31, 2017 Company
Business Acquisition [Line Items]
Number of physician group practices acquired \| Company		9	10
Number of neonatology practices acquired \| Company		2	1
Number of other pediatric subspecialty practices acquired \| Company		2	2
Number of radiology practices acquired \| Company		5	4
Total business acquisition consideration		$ 111.8
Contingent consideration payments related to prior-period acquisitions		6.4
Purchase consideration payments related to prior-period acquisitions		1.2
Change in the fair value of a contingent consideration		(5.3)
Assets held for sale		$ 46.0
Sale of equity method investments		49.00%
Number of maternal-fetal medicine practices acquired \| Company			2
Number of pediatric multi-specialty practice acquired \| Company			1
Sale of minority interest percentage	75.00%
Deconsolidation percentage	100.00%
Physician Group [Member]
Business Acquisition [Line Items]
Goodwill		$ 95.0
Other intangible assets		17.2
Decrease in current assets		1.7
Other liabilities		2.1
Prior-Period Acquisitions [Member]
Business Acquisition [Line Items]
Decrease in current assets		1.2
Decrease in noncurrent assets		1.5
Decrease in noncurrent liabilities		0.2
Net increase in goodwill resulting from finalization of tax acquisition accounting		4.0
Additional cash consideration related to a working capital true up		$ 1.5

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 4,382,995	$ 4,283,963
Change in goodwill carrying amount	99,000
Goodwill deductible for tax purpose	63,000
Intangible assets related to acquisitions	17,200
Amortization expense for intangible assets	$ 72,800	$ 68,900	$ 60,300
Physician And Hospital Agreements [Member]
Goodwill And Other Intangible Assets [Line Items]
Weighted average amortization period	9 years
Management Services Reporting Unit [Member]
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 321,600

Goodwill and Intangible Assets - Summary of Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 910,888	$ 906,681
Accumulated Amortization	(322,576)	(266,753)
Net Carrying Value	588,312	639,928
Physician And Hospital Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	376,871	381,635
Accumulated Amortization	(223,589)	(203,915)
Net Carrying Value	153,282	177,720
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	443,300	443,300
Accumulated Amortization	(71,870)	(48,837)
Net Carrying Value	371,430	394,463
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	43,156	43,156
Accumulated Amortization	(4,630)	(2,933)
Net Carrying Value	38,526	40,223
Patented and Other Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	47,561	38,590
Accumulated Amortization	(22,487)	(11,068)
Net Carrying Value	$ 25,074	$ 27,522

Goodwill and Intangible Assets - Amortization Expenses for Existing Intangible Assets for the Next Five Years (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for existing other intangible assets, 2019	$ 66,532
Amortization expense for existing other intangible assets, 2020	59,969
Amortization expense for existing other intangible assets, 2021	53,771
Amortization expense for existing other intangible assets, 2022	46,249
Amortization expense for existing other intangible assets, 2023	$ 40,448

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts payable	$ 31,059	$ 34,632
Accrued salaries and bonuses	249,834	225,429
Accrued payroll taxes and benefits	80,369	75,672
Accrued professional liabilities	34,931	37,912
Accrued contingent consideration	18,760	6,259
Accrued interest	9,477	4,495
Other accrued expenses	44,912	53,618
Accounts payable and accrued expenses, total	$ 469,342	$ 438,017

Accrued Professional Liabilities - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Total accrued professional liability	$ 243,991	$ 250,187	$ 202,052	$ 202,527
Accrued professional liability incurred but loss reserves not reported for claims	139,100	138,500
Accrued professional liability incurred and loss reserves reported for claims	104,900	111,700
Accrued professional liabilities	34,931	$ 37,912
Insurance receivables	$ 16,700

Accrued Professional Liabilities - Schedule of Accrued Professional Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Balance at beginning of year	$ 250,187	$ 202,052	$ 202,527
Assumed liabilities through acquisition	1,276	20,716
Provision (adjustment) for losses related to Current year	34,483	41,291	38,129
Provision (adjustment) for losses related to Prior years	10,299	9,983	(25,428)
Total provision for losses	44,782	51,274	12,701
Claim payments related to Current year	(555)	(712)	(766)
Claim payments related to Prior years	(51,699)	(23,143)	(12,410)
Total payments	(52,254)	(23,855)	(13,176)
Balance at end of year	$ 243,991	$ 250,187	$ 202,052

Line of Credit, Long-Term Debt and Capital Lease Obligations - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Nov. 30, 2018	Dec. 31, 2017	Dec. 31, 2015
Debt Instrument [Line Items]
Line of Credit facility, maturity date	Oct. 31, 2022
Long term debt	$ 1,969,818,000		$ 1,846,133,000
Letters of credit outstanding amount	200,000
Line of Credit facility, available balance	$ 1,300,000,000
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%			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	$ 1,234,592,000		$ 740,497,000
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 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%
6.25% Senior Unsecured Notes Due 2027 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt		$ 500,000,000
Debt instrument interest rate	6.25%	6.25%
Debt instrument maturity date description	Payable semi-annually in arrears on January 15 and July 15
Debt instrument, maturity year	2027
6.25% Senior Unsecured Notes Due 2027 [Member] \| Change In Control [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.00%
6.25% Senior Unsecured Notes Due 2027 [Member] \| Redemption Before 2022 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	100.00%
6.25% Senior Unsecured Notes Due 2027 [Member] \| Redemption Before 2022 [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	106.25%
6.25% Senior Unsecured Notes Due 2027 [Member] \| Redemption in 2022 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	104.688%
6.25% Senior Unsecured Notes Due 2027 [Member] \| Redemption in 2023 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	103.125%
6.25% Senior Unsecured Notes Due 2027 [Member] \| Redemption in 2024 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.563%
6.25% Senior Unsecured Notes Due 2027 [Member] \| Redemption in 2025 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, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt instrument principal amount	$ 1,989,500	$ 1,860,500
Unamortized debt issuance cost	(19,682)	(14,367)
Long term debt	1,969,818	1,846,133
5.25% Senior Unsecured Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	1,250,000	750,000
Unamortized debt issuance cost	(15,408)	(9,503)
Long term debt	1,234,592	740,497
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	739,500	1,110,500
Unamortized debt issuance cost	(4,274)	(4,864)
Long term debt	$ 735,226	$ 1,105,636

Line of Credit, Long-Term Debt and Capital Lease Obligations - Schedule of Capital Lease Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Capital lease obligations	$ 441	$ 1,826
Less: Current portion	(253)	(1,401)
Long-term portion	$ 188	$ 425

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, 2018 USD ($)
Debt Disclosure [Abstract]
2019	$ 253
2020	114
2021	$ 74

Income Taxes - Summary of Components of Income Tax Provision (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal, Current									$ 97,754	$ 130,053	$ 166,758
Federal, Deferred									(20,176)	(63,038)	15,596
Federal income tax provision, Total									77,578	67,015	182,354
State, Current									26,605	20,070	4,296
State, Deferred									(3,973)	2,965	2,553
State income tax provision, Total									22,632	23,035	6,849
Income tax provision, Total	$ 21,156	$ 24,873	$ 30,122	$ 24,059	$ (27,761)	$ 42,119	$ 40,725	$ 34,967	$ 100,210	$ 90,050	$ 189,203

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Income Tax [Line Items]
Tax at statutory rate										21.00%	35.00%	35.00%
Effective tax rate										27.17%	21.94%	36.80%
Income tax benefit resulting from the reduction of deferred tax liabilities					$ (70,000)
Effective income tax rate favorable impact of change in uncertain tax positions													$ 10,600
Increase (decrease) in net deferred tax liability										$ (23,600)
Increase in allowance for uncollectible accounts										114,800
Accounting method changes	$ 109,418				4,150					109,418	$ 4,150
Decrease in accrual to cash adjustment										31,300
Adjustment to additional paid-in capital for excess tax benefits related to stock-based awards												$ 4,200
Income tax expense for excess tax deficiencies										1,400	200
Net operating loss carryforwards for federal and state tax	101,900				116,000					101,900	116,000	130,000
Operating loss carryforwards subject to expiration	74,300									74,300
Operating loss carryforwards not subject to expiration	27,600									27,600
Uncertain tax position liability	11,185				10,972					11,185	10,972	9,469		$ 18,447
Unrecognized tax benefits that would impact effective tax rate	10,900									10,900
Increase (decrease) in uncertain tax position										200	1,500
Income tax expense (benefit)	21,156	$ 24,873	$ 30,122	$ 24,059	(27,761)	$ 42,119	$ 40,725	$ 34,967		100,210	90,050	189,203
Company's accrued liability for interest and penalties related to income tax liabilities	1,100				$ 1,200					$ 1,100	1,200
Interest and Penalties [Member]
Income Tax [Line Items]
Income tax expense (benefit)											$ 200	$ 7,900
Earliest Tax Year [Member]
Income Tax [Line Items]
Federal and state income tax examinations										2014
Latest Tax Year [Member]
Income Tax [Line Items]
Federal and state income tax examinations											2017
Internal Revenue Code Section 481 [Member]
Income Tax [Line Items]
Accounting method changes	$ 105,300									$ 105,300
Scenario, Forecast [Member]
Income Tax [Line Items]
Increase (decrease) in uncertain tax position									$ 200
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										2038

Income Taxes - Schedule of Differences Between Effective Rate and United States Federal Income Tax Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax at statutory rate	21.00%	35.00%	35.00%
State income tax, net of federal benefit	4.80%	3.33%	2.94%
Non-deductible expenses	0.44%	0.49%	0.43%
Change in accrual estimates relating to uncertain tax positions	0.05%	0.02%	(2.11%)
Change in valuation allowance			0.48%
Other, net	1.20%	0.16%	0.06%
Change in tax law	(0.32%)	(17.06%)
Income tax provision	27.17%	21.94%	36.80%

Income Taxes - Significant Components of Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Allowance for uncollectible accounts	$ 194,876	$ 80,056
Reserves and accruals	59,270	45,454
Stock-based compensation	9,201	7,975
Net operating loss carryforward	25,226	28,569
Property and equipment	26	685
Other	1,197	970
Deferred tax assets before valuation allowance	289,796	163,709
Less: Valuation allowance	(2,628)	(2,615)
Deferred tax assets, net of valuation allowance	287,168	161,094
Gross deferred tax liabilities:
Amortization	(286,552)	(258,618)
Accounting method changes	(109,418)	(4,150)
Accrual to cash adjustment	(39)	(31,290)
Other	(489)
Total deferred tax liabilities	(396,498)	(294,058)
Net deferred tax liability	$ (109,330)	$ (132,964)

Income Taxes - Schedule of Activity Related to Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 10,972	$ 9,469	$ 18,447
Increases related to prior year tax positions	385	2,284	301
Decreases related to prior year tax positions		(143)	(3,927)
Increases related to current year tax positions	2,900	1,430	2,258
Settlements			(5,644)
Decreases related to lapse of statutes of limitation	(3,072)	(2,068)	(1,966)
Balance at end of year	$ 11,185	$ 10,972	$ 9,469

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Weighted average number of common shares outstanding	87,810	90,984	92,987	92,859	92,756	92,589	92,181	92,360	91,104	92,431	92,422
Weighted average number of dilutive common share equivalents									502	527	687
Weighted average number of common and common equivalent shares outstanding	88,258	91,359	93,529	93,505	93,159	92,881	92,812	93,143	91,606	92,958	93,109
Antidilutive securities not included in the diluted net income per common share calculation									214	107	2

Stock Incentive Plans and Stock Purchase Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	$ 38,700,000	$ 29,600,000	$ 34,000,000
Aggregate fair value of restricted and deferred stocks vested	$ 27,400,000	$ 29,300,000	$ 29,800,000
Weighted average grant-date fair value of restricted and deferred stock awards granted	$ 51.99	$ 54.22	$ 67.90
Aggregate intrinsic value of stock options exercised	$ 2,800,000	$ 5,500,000	$ 6,800,000
Excess tax benefit related to employee stock incentive plans	0		4,131,000
Cash proceeds received from the exercise of stock options	$ 3,700,000	$ 4,800,000	$ 4,700,000
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 4 months 24 days
Unrecognized compensation expense related to non-vested restricted shares	$ 30,800,000
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] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants and awards under Stock Incentive Plans	2,000,000
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]
Common stock, aggregate shares authorized	2,600,000
Aggregate number Shares issued under Stock Purchase Plans	400,000
Common stock, reserved for issuance	1,600,000

Stock Incentive Plans and Stock Purchase Plans - Schedule of Restricted Stock and Deferred Stock Awards (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Non-vested shares at January 1, 2018	1,041,034
Number of Shares, Awarded	770,480
Number of Shares, Forfeited	(69,293)
Number of Shares, Vested	(431,368)
Number of Shares, Non-vested shares at December 31, 2018	1,310,853	1,041,034
Weighted Average Fair Value, Non-vested shares at January 1, 2018	$ 60.21
Weighted Average Fair Value, Awarded	51.99	$ 54.22	$ 67.90
Weighted Average Fair Value, Forfeited	56.65
Weighted Average Fair Value, Vested	63.57
Weighted Average Fair Value, Non-vested shares at December 31, 2018	$ 54.46	$ 60.21

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Outstanding at January 1, 2018	246,342
Number of Shares, Exercised	(133,366)
Number of Shares, Outstanding at December 31, 2018	112,976	246,342
Number of Shares, Exercisable at December 31, 2017	112,976
Weighted Average Exercise Price, Outstanding at January 1, 2018	$ 27.51
Weighted Average Exercise Price, Exercised	27.38
Weighted Average Exercise Price, Outstanding at December 31, 2018	27.65	$ 27.51
Weighted Average Exercise Price, Exercisable at December 31, 2018	$ 27.65
Weighted Average Remaining Contractual Term (in years), Outstanding at December 31, 2018	1 year 3 months 18 days
Weighted Average Remaining Contractual Term (in years), Exercisable at December 31, 2018	1 year 3 months 18 days
Aggregate Intrinsic Value, Exercised	$ 2.8	$ 5.5	$ 6.8
Aggregate Intrinsic Value, Outstanding at December 31, 2018	0.7
Aggregate Intrinsic Value, Exercisable at December 31, 2018	$ 0.7

Common Stock Repurchase Programs - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 04, 2018	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Aug. 31, 2018
Common Stock [Line Items]
Common stock authorized for repurchase							$ 500,000,000
Common stock repurchased				$ 302,160,000	$ 70,192,000	$ 61,828,000
Common Stock [Member]
Common Stock [Line Items]
Common stock repurchased				$ 70,000	$ 10,000	$ 9,000
Repurchased common stock, shares				7,041,000	1,038,000	946,000
Restricted Stock [Member]
Common Stock [Line Items]
Number of shares withheld to satisfy minimum statutory tax withholding obligations			54,909		38,257
Amount withheld to satisfy minimum statutory tax withholding obligations			$ 2,500,000		$ 2,100,000
Accelerated Share Repurchase (ASR) Agreements [Member]
Common Stock [Line Items]
Common stock purchase							$ 250,000,000
Common stock repurchased	$ 250,000,000
Repurchased common stock, shares	4,200,000	1,700,000

Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 30,824
2020	22,038
2021	17,946
2022	12,708
2023	9,440
Thereafter	10,522
Total	$ 103,478

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 932,696	$ 896,652	$ 915,918	$ 901,857	$ 910,820	$ 868,951	$ 842,944	$ 835,597	$ 3,647,123	$ 3,458,312	$ 3,183,159
Practice salaries and benefits	657,061	625,717	620,980	631,830	617,455	586,476	561,418	572,385	2,535,588	2,337,734	2,031,220
Practice supplies and other operating expenses	29,381	30,159	31,833	30,655	32,353	29,497	30,872	27,796	122,028	120,518	118,416
General and administrative expenses	112,789	102,905	107,908	108,776	108,895	101,430	103,015	103,765	432,378	417,105	372,572
Depreciation and amortization	29,891	28,709	26,518	26,163	26,414	25,116	25,735	25,614	111,281	102,879	89,264
Total operating expenses	829,122	787,490	787,239	797,424	785,117	742,519	721,040	729,560	3,201,275	2,978,236	2,611,472
Income from operations	103,574	109,162	128,679	104,433	125,703	126,432	121,904	106,037	445,848	480,076	571,687
Investment and other income	967	1,302	1,202	1,464	2,777	235	365	576	4,935	3,953	2,019
Interest expense	(25,448)	(21,782)	(21,604)	(19,935)	(19,844)	(18,428)	(18,535)	(17,752)	(88,769)	(74,559)	(63,092)
Equity (loss) in earnings of unconsolidated affiliate	2,277	1,766	1,257	1,525	(294)	(240)	689	797	6,825	952	3,185
Total non-operating expenses	(22,204)	(18,714)	(19,145)	(16,946)	(17,361)	(18,433)	(17,481)	(16,379)	(77,009)	(69,654)	(57,888)
Income before income taxes	81,370	90,448	109,534	87,487	108,342	107,999	104,423	89,658	368,839	410,422	513,799
Income tax (provision) benefit	(21,156)	(24,873)	(30,122)	(24,059)	27,761	(42,119)	(40,725)	(34,967)	(100,210)	(90,050)	(189,203)
Net income	0	0	0	0					268,629	320,372	324,596
Net loss attributable to noncontrolling interests	0	0	0	0							318
Net income attributable to MEDNAX, Inc.	$ 60,214	$ 65,575	$ 79,412	$ 63,428	$ 136,103	$ 65,880	$ 63,698	$ 54,691	$ 268,629	$ 320,372	$ 324,914
Earnings per share, Basic	$ 0.69	$ 0.72	$ 0.85	$ 0.68	$ 1.47	$ 0.71	$ 0.69	$ 0.59	$ 2.95	$ 3.47	$ 3.52
Earnings per share, Diluted	$ 0.68	$ 0.72	$ 0.85	$ 0.68	$ 1.46	$ 0.71	$ 0.69	$ 0.59	$ 2.93	$ 3.45	$ 3.49
Weighted average shares, Basic	87,810	90,984	92,987	92,859	92,756	92,589	92,181	92,360	91,104	92,431	92,422
Weighted average shares, Diluted	88,258	91,359	93,529	93,505	93,159	92,881	92,812	93,143	91,606	92,958	93,109

Retirement Plans	12 Months Ended
Retirement Plans	Dec. 31, 2018
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 $55.8 million, $50.7 million and $45.2 million for the years ended December 31, 2018, 2017 and 2016, respectively, primarily related to the 401(k) Plans.

Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Expense of retirement plans related to the 401(k) Plans	$ 55.8	$ 50.7	$ 45.2

Line of Credit, Long-Term Debt and Capital Lease Obligations - Summary of Estimated Fair Value of Notes (Detail) - Level 2 [Member] - Estimate of Fair Value Measurement [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
5.25% Senior Unsecured Notes Due 2023 [Member]
Debt Instrument Fair Value [Line Items]
Estimated fair value	$ 736,725	$ 763,125
6.25% Senior Unsecured Notes Due 2027 [Member]
Debt Instrument Fair Value [Line Items]
Estimated fair value	$ 482,500