Schedule of Disaggregates Revenue by Major Source (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Net revenues		$ 3,086,935	$ 2,912,541	$ 2,729,754	$ 2,829,667	$ 2,896,247	$ 2,822,453	$ 2,855,168	$ 2,804,391	$ 11,558,897	$ 11,378,259	$ 10,772,278
Acute Care Hospital Services
Disaggregation Of Revenue [Line Items]
Net revenues										6,337,304	6,164,560	5,719,905
Acute Care Hospital Services | CARES Act and Other Grant Revenue
Disaggregation Of Revenue [Line Items]
Net revenues										316,000
Behavioral Health Services
Disaggregation Of Revenue [Line Items]
Net revenues	[1]									5,208,722	$ 5,210,063	$ 5,038,874
Behavioral Health Services | CARES Act and Other Grant Revenue
Disaggregation Of Revenue [Line Items]
Net revenues										$ 97,000

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $584 million in 2020, $554 million in 2019 and $505 million in 2018.  Total assets at our U.K. behavioral health care facilities were approximately $1.334 billion as of December 31, 2020, $1.270 billion as of December 31, 2019 and $1.224 billion as of December 31, 2018. In addition, included in our 2019 Behavioral Health Services operating segment Income (loss) before allocation of corporate overhead and income taxes is a pre-tax $98 million provision for asset impairment to reduce the carrying value of a tradename intangible asset and real property assets. Included in our 2018 Behavioral Health Services operating segment Income (loss) before allocation of corporate overhead and income taxes is a pre-tax $49 million provision for asset impairment to reduce the carrying value of a tradename intangible asset.