Segment Reporting (Parenthetical) (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]
Net revenues		$ 3,155,999	$ 2,912,541	$ 9,366,866	$ 8,471,962
Total assets		12,846,853	12,975,758	12,846,853	12,975,758	$ 13,476,879
Behavioral Health Services
Segment Reporting Information [Line Items]
Net revenues	[1]	1,328,293	1,299,591	4,075,127	3,864,823
Total assets	[1]	7,106,832	6,898,757	7,106,832	6,898,757
Behavioral Health Services | Located in U.K.
Segment Reporting Information [Line Items]
Net revenues		174,000	155,000	511,000	429,000
Total assets		$ 1,338,000	$ 1,257,000	$ 1,338,000	$ 1,257,000

[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.