Segment Reporting (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Gross inpatient revenues		$ 11,968,376	$ 10,624,832	$ 34,751,236	$ 29,993,979
Gross outpatient revenues		5,586,222	4,372,149	16,037,922	12,924,483
Total net revenues		3,155,999	2,912,541	9,366,866	8,471,962
Income/(loss) before allocation of corporate overhead and income taxes		286,890	323,264	986,565	849,705
Allocation of corporate overhead			0	0	0
Income before income taxes		286,890	323,264	986,565	849,705
Total assets		12,846,853	12,975,758	12,846,853	12,975,758	$ 13,476,879
Acute Care Hospital Services
Segment Reporting Information [Line Items]
Gross inpatient revenues		9,497,975	8,137,264	27,279,494	22,695,513
Gross outpatient revenues		5,343,246	4,128,549	15,281,854	12,204,970
Total net revenues		1,822,027	1,610,003	5,271,000	4,598,558
Income/(loss) before allocation of corporate overhead and income taxes		208,638	177,606	600,419	464,139
Allocation of corporate overhead		(58,452)	(55,980)	(174,786)	(167,936)
Income before income taxes		150,186	121,626	425,633	296,203
Total assets		5,295,533	4,666,917	5,295,533	4,666,917
Behavioral Health Services
Segment Reporting Information [Line Items]
Gross inpatient revenues	[1]	2,470,401	2,487,568	7,471,742	7,298,466
Gross outpatient revenues	[1]	242,976	243,600	756,068	719,513
Total net revenues	[1]	1,328,293	1,299,591	4,075,127	3,864,823
Income/(loss) before allocation of corporate overhead and income taxes	[1]	197,779	252,532	753,681	746,980
Allocation of corporate overhead	[1]	(43,120)	(42,667)	(129,169)	(128,147)
Income before income taxes	[1]	154,659	209,865	624,512	618,833
Total assets	[1]	7,106,832	6,898,757	7,106,832	6,898,757
Other
Segment Reporting Information [Line Items]
Gross inpatient revenues			0		0
Gross outpatient revenues			0		0
Total net revenues		5,679	2,947	20,739	8,581
Income/(loss) before allocation of corporate overhead and income taxes		(119,527)	(106,874)	(367,535)	(361,414)
Allocation of corporate overhead		101,572	98,647	303,955	296,083
Income before income taxes		(17,955)	(8,227)	(63,580)	(65,331)
Total assets		$ 444,488	$ 1,410,084	$ 444,488	$ 1,410,084

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $174 million and $155 million for the three-month periods ended September 30, 2021 and 2020, respectively, and approximately $511 million and $429 million for the nine-month periods ended September 30, 2021 and 2020, respectively.  Total assets at our U.K. behavioral health care facilities were approximately $1.338 billion and $1.257 billion as of September 30, 2021 and 2020, respectively.