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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 741,740	$ 722,273	$ 676,588	$ 639,395	$ 650,525	$ 626,506	$ 595,544	$ 566,338	$ 2,779,996	$ 2,438,913	$ 2,154,012
Practice salaries and benefits	461,074	450,033	422,803	419,595	404,345	394,794	372,216	372,040	1,753,505	1,543,395	1,361,318
Practice supplies and other operating expenses	26,164	24,007	24,878	23,431	23,549	21,570	22,466	21,417	98,480	89,002	82,388
General and administrative expenses	85,393	80,185	72,401	67,936	67,641	60,643	60,829	58,414	305,915	247,527	218,209
Depreciation and amortization	18,149	16,918	15,549	13,612	13,903	11,356	10,361	10,370	64,228	45,990	39,966
Total operating expenses	590,780	571,143	535,631	524,574	509,438	488,363	465,872	462,241	2,222,128	1,925,914	1,701,881
Income from operations	150,960	151,130	140,957	114,821	141,087	138,143	129,672	104,097	557,868	512,999	452,131
Investment and other income	751	567	384	142	195	563	335	1,635	1,844	2,728	1,696
Interest expense	(8,493)	(6,201)	(5,149)	(3,267)	(3,313)	(2,019)	(2,188)	(1,371)	(23,110)	(8,891)	(5,415)
Equity in earnings of unconsolidated affiliate	777	784	745	821	905	725	150		3,127	1,780
Total non-operating expenses	(6,965)	(4,850)	(4,020)	(2,304)	(2,213)	(731)	(1,703)	264	(18,139)	(4,383)	(3,719)
Income before income taxes	143,995	146,280	136,937	112,517	138,874	137,412	127,969	104,361	539,729	508,616	448,412
Income tax provision	51,581	55,640	52,889	43,928	50,594	51,174	48,944	40,701	204,038	191,413	167,895
Net income	92,414	90,640	84,048	68,589	88,280	86,238	79,025	63,660	335,691	317,203	280,517
Net (income) loss attributable to noncontrolling interests	288	141	82	118	118	(31)	(9)		629	78
Net income attributable to MEDNAX, Inc.	$ 92,702	$ 90,781	$ 84,130	$ 68,707	$ 88,398	$ 86,207	$ 79,016	$ 63,660	$ 336,320	$ 317,281	$ 280,517
Earnings per share, Basic	$ 1.00	$ 0.98	$ 0.91	$ 0.73	$ 0.90	$ 0.87	$ 0.80	$ 0.64	$ 3.61	$ 3.22	$ 2.83
Earnings per share, Diluted	$ 0.99	$ 0.97	$ 0.90	$ 0.72	$ 0.89	$ 0.86	$ 0.79	$ 0.63	$ 3.58	$ 3.18	$ 2.78
Weighted average shares, Basic	92,790	92,949	92,500	94,231	98,066	99,088	98,411	99,076	93,077	98,588	99,112
Weighted average shares, Diluted	93,536	93,646	93,495	95,325	99,129	100,145	99,866	100,696	93,960	99,887	100,969