Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Gross inpatient revenues	$ 5,992,494	$ 5,294,869	$ 18,198,689	$ 16,190,953
Gross outpatient revenues	2,646,789	2,259,152	7,772,238	6,690,163
Total net revenues	2,227,655	2,038,717	6,728,212	6,028,797
Income/(loss) before allocation of corporate overhead and income taxes	248,027	144,478	852,752	638,606
Allocation of corporate overhead	0	0	0	0
Income/(loss) after allocation of corporate overhead and before income taxes	248,027	144,478	852,752	638,606
Total assets	9,206,878	8,961,592	9,206,878	8,961,592	$ 8,974,443
Acute Care Hospital Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	4,115,598	3,616,647	12,633,298	11,217,320
Gross outpatient revenues	2,444,456	2,058,148	7,132,212	6,083,715
Total net revenues	1,136,341	1,042,647	3,446,797	3,054,359
Income/(loss) before allocation of corporate overhead and income taxes	91,784	100,388	387,568	330,382
Allocation of corporate overhead	(49,426)	(44,698)	(148,274)	(134,088)
Income/(loss) after allocation of corporate overhead and before income taxes	42,358	55,690	239,294	196,294
Total assets	3,391,193	3,321,166	3,391,193	3,321,166
Behavioral Health Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	1,876,896	1,678,222	5,565,391	4,973,633
Gross outpatient revenues	202,333	192,032	623,915	580,627
Total net revenues	1,089,509	992,461	3,272,714	2,964,047
Income/(loss) before allocation of corporate overhead and income taxes	249,812	228,710	771,667	693,399
Allocation of corporate overhead	(29,526)	(24,750)	(88,913)	(74,055)
Income/(loss) after allocation of corporate overhead and before income taxes	220,286	203,960	682,754	619,344
Total assets	5,458,647	5,429,453	5,458,647	5,429,453
Other
Segment Reporting Information [Line Items]
Gross outpatient revenues		8,972	16,111	25,821
Total net revenues	1,805	3,609	8,701	10,391
Income/(loss) before allocation of corporate overhead and income taxes	(93,569)	(184,620)	(306,483)	(385,175)
Allocation of corporate overhead	78,952	69,448	237,187	208,143
Income/(loss) after allocation of corporate overhead and before income taxes	(14,617)	(115,172)	(69,296)	(177,032)
Total assets	$ 357,038	$ 210,973	$ 357,038	$ 210,973