Segment Reporting (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross inpatient revenues		$ 7,680,132	$ 6,678,674	$ 15,460,984	$ 13,603,781
Gross outpatient revenues		3,544,242	3,068,095	7,084,879	6,057,067
Total net revenues		2,612,356	2,430,855	5,225,214	4,880,653
Income/(loss) before allocation of corporate overhead and income taxes		294,271	302,846	612,697	629,570
Allocation of corporate overhead		0	0	0	0
Income/(loss) after allocation of corporate overhead and before income taxes		294,271	302,846	612,697	629,570
Total assets		10,552,487	9,540,930	10,552,487	9,540,930	$ 10,317,802
Acute Care Hospital Services
Segment Reporting Information [Line Items]
Gross inpatient revenues		5,430,997	4,682,682	11,028,847	9,648,219
Gross outpatient revenues		3,286,930	2,838,852	6,581,107	5,606,181
Total net revenues		1,366,457	1,253,328	2,756,004	2,540,475
Income/(loss) before allocation of corporate overhead and income taxes		157,877	137,372	345,681	323,290
Allocation of corporate overhead		(45,675)	(42,691)	(91,351)	(85,340)
Income/(loss) after allocation of corporate overhead and before income taxes		112,202	94,681	254,330	237,950
Total assets		3,754,983	3,497,571	3,754,983	3,497,571
Behavioral Health Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	[1]	2,249,135	1,995,992	4,432,137	3,955,562
Gross outpatient revenues	[1]	257,312	229,243	503,772	450,886
Total net revenues	[1]	1,242,561	1,174,755	2,460,683	2,335,801
Income/(loss) before allocation of corporate overhead and income taxes	[1]	252,146	272,916	504,077	538,501
Allocation of corporate overhead	[1]	(39,653)	(38,726)	(79,314)	(77,442)
Income/(loss) after allocation of corporate overhead and before income taxes	[1]	212,493	234,190	424,763	461,059
Total assets	[1]	6,541,328	5,920,483	6,541,328	5,920,483
Other
Segment Reporting Information [Line Items]
Gross inpatient revenues		0	0	0	0
Gross outpatient revenues		0	0	0	0
Total net revenues		3,338	2,772	8,527	4,377
Income/(loss) before allocation of corporate overhead and income taxes		(115,752)	(107,442)	(237,061)	(232,221)
Allocation of corporate overhead		85,328	81,417	170,665	162,782
Income/(loss) after allocation of corporate overhead and before income taxes		(30,424)	(26,025)	(66,396)	(69,439)
Total assets		$ 256,176	$ 122,876	$ 256,176	$ 122,876

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $106 million and $64 million for the three-month periods ended June 30, 2017 and 2016, respectively, and approximately $206 million and $125 million for the six-month periods ended June 30, 2017 and 2016, respectively. Total assets at our U.K. behavioral health care facilities were approximately $1,028 million and $490 million as of June 30, 2017 and 2016, respectively.