Schedule of Disaggregates Revenue by Major Source (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Net revenues		$ 3,155,999	$ 2,912,541	$ 9,366,866	$ 8,471,962
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 406,702	$ 439,950	$ 1,231,645	$ 1,256,473
Percentage of Net Revenue		13.00%	15.00%	13.00%	15.00%
Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 346,923	$ 296,787	$ 1,015,950	$ 820,766
Percentage of Net Revenue		11.00%	10.00%	11.00%	10.00%
Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 283,270	$ 320,427	$ 945,280	$ 908,946
Percentage of Net Revenue		9.00%	11.00%	10.00%	11.00%
Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 503,286	$ 443,662	$ 1,469,005	$ 1,258,875
Percentage of Net Revenue		16.00%	15.00%	16.00%	15.00%
Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 1,023,671	$ 907,052	$ 2,932,177	$ 2,514,295
Percentage of Net Revenue		32.00%	31.00%	31.00%	30.00%
UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 173,728	$ 155,323	$ 510,614	$ 428,795
Percentage of Net Revenue		6.00%	5.00%	5.00%	5.00%
Other Patient Revenue and Adjustments, Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 187,377	$ 183,510	$ 615,011	$ 570,500
Percentage of Net Revenue		6.00%	6.00%	7.00%	7.00%
Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 231,042	$ 165,830	$ 647,184	$ 713,312
Percentage of Net Revenue		7.00%	6.00%	7.00%	8.00%
Acute Care Hospital Services
Disaggregation Of Revenue [Line Items]
Net revenues		$ 1,822,027	$ 1,610,003	$ 5,271,000	$ 4,598,558
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Acute Care Hospital Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 310,483	$ 319,259	$ 954,207	$ 909,594
Percentage of Net Revenue		17.00%	20.00%	18.00%	20.00%
Acute Care Hospital Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 280,674	$ 234,169	$ 830,627	$ 638,931
Percentage of Net Revenue		15.00%	15.00%	16.00%	14.00%
Acute Care Hospital Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 136,989	$ 160,671	$ 418,335	$ 420,082
Percentage of Net Revenue		8.00%	10.00%	8.00%	9.00%
Acute Care Hospital Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 176,497	$ 126,979	$ 473,256	$ 358,770
Percentage of Net Revenue		10.00%	8.00%	9.00%	8.00%
Acute Care Hospital Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 674,396	$ 585,333	$ 1,862,012	$ 1,558,765
Percentage of Net Revenue		37.00%	36.00%	35.00%	34.00%
Acute Care Hospital Services | UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 0	$ 0	$ 0	$ 0
Percentage of Net Revenue		0.00%	0.00%	0.00%	0.00%
Acute Care Hospital Services | Other Patient Revenue and Adjustments, Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 69,935	$ 56,188	$ 248,342	$ 198,983
Percentage of Net Revenue		4.00%	3.00%	5.00%	4.00%
Acute Care Hospital Services | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 173,053	$ 127,404	$ 484,221	$ 513,433
Percentage of Net Revenue		9.00%	8.00%	9.00%	11.00%
Behavioral Health Services
Disaggregation Of Revenue [Line Items]
Net revenues	[1]	$ 1,328,293	$ 1,299,591	$ 4,075,127	$ 3,864,823
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Behavioral Health Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 96,219	$ 120,691	$ 277,438	$ 346,879
Percentage of Net Revenue		7.00%	9.00%	7.00%	9.00%
Behavioral Health Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 66,249	$ 62,618	$ 185,323	$ 181,835
Percentage of Net Revenue		5.00%	5.00%	5.00%	5.00%
Behavioral Health Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 146,281	$ 159,756	$ 526,945	$ 488,864
Percentage of Net Revenue		11.00%	12.00%	13.00%	13.00%
Behavioral Health Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 326,789	$ 316,683	$ 995,749	$ 900,105
Percentage of Net Revenue		25.00%	24.00%	24.00%	23.00%
Behavioral Health Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 349,275	$ 321,719	$ 1,070,165	$ 955,530
Percentage of Net Revenue		26.00%	25.00%	26.00%	25.00%
Behavioral Health Services | UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 173,728	$ 155,323	$ 510,614	$ 428,795
Percentage of Net Revenue		13.00%	12.00%	13.00%	11.00%
Behavioral Health Services | Other Patient Revenue and Adjustments, Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 117,442	$ 127,322	$ 366,669	$ 371,517
Percentage of Net Revenue		9.00%	10.00%	9.00%	10.00%
Behavioral Health Services | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 52,310	$ 35,479	$ 142,224	$ 191,298
Percentage of Net Revenue		4.00%	3.00%	3.00%	5.00%
Other
Disaggregation Of Revenue [Line Items]
Net revenues		$ 5,679	$ 2,947	$ 20,739	$ 8,581
Other | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 5,679	$ 2,947	$ 20,739	$ 8,581

[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.