Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Gross inpatient revenues	$ 6,679,446	$ 5,992,494	$ 20,283,227	$ 18,198,689
Gross outpatient revenues	3,072,422	2,646,789	9,129,489	7,772,238
Total net revenues	2,409,872	2,227,655	7,290,525	6,728,212
Income/(loss) before allocation of corporate overhead and income taxes	245,440	248,027	875,010	852,752
Allocation of corporate overhead	0	0	0	0
Income/(loss) after allocation of corporate overhead and before income taxes	245,440	248,027	875,010	852,752
Total assets	9,673,639	9,187,415	9,673,639	9,187,415	$ 9,615,444
Acute Care Hospital Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	4,647,578	4,115,598	14,295,797	12,633,298
Gross outpatient revenues	2,854,851	2,444,456	8,461,032	7,132,212
Total net revenues	1,253,866	1,136,341	3,794,341	3,446,797
Income/(loss) before allocation of corporate overhead and income taxes	97,542	91,784	420,832	387,568
Allocation of corporate overhead	(42,667)	(49,426)	(128,007)	(148,274)
Income/(loss) after allocation of corporate overhead and before income taxes	54,875	42,358	292,825	239,294
Total assets	3,581,425	3,391,193	3,581,425	3,391,193
Behavioral Health Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	2,031,868	1,876,896	5,987,430	5,565,391
Gross outpatient revenues	217,571	202,333	668,457	623,915
Total net revenues	1,153,880	1,089,509	3,489,681	3,272,714
Income/(loss) before allocation of corporate overhead and income taxes	245,515	249,812	784,016	771,667
Allocation of corporate overhead	(38,719)	(29,526)	(116,161)	(88,913)
Income/(loss) after allocation of corporate overhead and before income taxes	206,796	220,286	667,855	682,754
Total assets	5,927,564	5,458,647	5,927,564	5,458,647
Other
Segment Reporting Information [Line Items]
Gross inpatient revenues	0	0	0	0
Gross outpatient revenues	0	0	0	16,111
Total net revenues	2,126	1,805	6,503	8,701
Income/(loss) before allocation of corporate overhead and income taxes	(97,617)	(93,569)	(329,838)	(306,483)
Allocation of corporate overhead	81,386	78,952	244,168	237,187
Income/(loss) after allocation of corporate overhead and before income taxes	(16,231)	(14,617)	(85,670)	(69,296)
Total assets	$ 164,650	$ 337,575	$ 164,650	$ 337,575