Segment Reporting (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross inpatient revenues		$ 7,601,856	$ 6,679,446	$ 23,062,840	$ 20,283,227
Gross outpatient revenues		3,435,625	3,072,422	10,520,504	9,129,489
Total net revenues		2,541,864	2,409,872	7,767,078	7,290,525
Income/(loss) before allocation of corporate overhead and income taxes		220,354	245,440	833,051	875,010
Allocation of corporate overhead		0	0	0	0
Income/(loss) after allocation of corporate overhead and before income taxes		220,354	245,440	833,051	875,010
Total assets		10,639,360	9,673,639	10,639,360	9,673,639	$ 10,317,802
Acute Care Hospital Services
Segment Reporting Information [Line Items]
Gross inpatient revenues		5,344,625	4,647,578	16,373,472	14,295,797
Gross outpatient revenues		3,199,066	2,854,851	9,780,173	8,461,032
Total net revenues		1,316,748	1,253,866	4,072,752	3,794,341
Income/(loss) before allocation of corporate overhead and income taxes		106,707	97,542	452,388	420,832
Allocation of corporate overhead		(45,680)	(42,667)	(137,031)	(128,007)
Income/(loss) after allocation of corporate overhead and before income taxes		61,027	54,875	315,357	292,825
Total assets		3,736,676	3,581,425	3,736,676	3,581,425
Behavioral Health Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	[1]	2,257,231	2,031,868	6,689,368	5,987,430
Gross outpatient revenues	[1]	236,559	217,571	740,331	668,457
Total net revenues	[1]	1,224,548	1,153,880	3,685,230	3,489,681
Income/(loss) before allocation of corporate overhead and income taxes	[1]	228,673	245,515	732,749	784,016
Allocation of corporate overhead	[1]	(39,707)	(38,719)	(119,021)	(116,161)
Income/(loss) after allocation of corporate overhead and before income taxes	[1]	188,966	206,796	613,728	667,855
Total assets	[1]	6,610,811	5,927,564	6,610,811	5,927,564
Other
Segment Reporting Information [Line Items]
Gross inpatient revenues		0	0	0	0
Gross outpatient revenues		0	0	0	0
Total net revenues		568	2,126	9,096	6,503
Income/(loss) before allocation of corporate overhead and income taxes		(115,026)	(97,617)	(352,086)	(329,838)
Allocation of corporate overhead		85,387	81,386	256,052	244,168
Income/(loss) after allocation of corporate overhead and before income taxes		(29,639)	(16,231)	(96,034)	(85,670)
Total assets		$ 291,873	$ 164,650	$ 291,873	$ 164,650

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $111 million and $60 million for the three-month periods ended September 30, 2017 and 2016, respectively, and approximately $317 million and $185 million for the nine-month periods ended September 30, 2017 and 2016, respectively. Total assets at our U.K. behavioral health care facilities were approximately $1.094 billion and $485 million as of September 30, 2017 and 2016, respectively.