Schedule of Disaggregates Revenue by Major Source (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation Of Revenue [Line Items]
Net revenues		$ 3,197,880	$ 2,729,754	$ 6,210,867	$ 5,559,421
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 400,938	$ 370,881	$ 824,943	$ 816,523
Percentage of Net Revenue		13.00%	14.00%	13.00%	15.00%
Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 335,925	$ 242,750	$ 669,027	$ 523,979
Percentage of Net Revenue		11.00%	9.00%	11.00%	9.00%
Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 397,229	$ 285,542	$ 662,010	$ 588,519
Percentage of Net Revenue		12.00%	10.00%	11.00%	11.00%
Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 495,463	$ 389,201	$ 965,719	$ 815,213
Percentage of Net Revenue		15.00%	14.00%	16.00%	15.00%
Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 960,952	$ 725,819	$ 1,908,506	$ 1,607,243
Percentage of Net Revenue		30.00%	27.00%	31.00%	29.00%
UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 172,220	$ 136,622	$ 336,886	$ 273,472
Percentage of Net Revenue		5.00%	5.00%	5.00%	5.00%
Other Patient Revenue and Adjustments, Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 213,101	$ 199,331	$ 427,634	$ 386,990
Percentage of Net Revenue		7.00%	7.00%	7.00%	7.00%
Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 222,052	$ 379,608	$ 416,142	$ 547,482
Percentage of Net Revenue		7.00%	14.00%	7.00%	10.00%
Acute Care Hospital Services
Disaggregation Of Revenue [Line Items]
Net revenues		$ 1,754,431	$ 1,467,506	$ 3,448,973	$ 2,988,555
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Acute Care Hospital Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 308,211	$ 264,310	$ 643,724	$ 590,335
Percentage of Net Revenue		18.00%	18.00%	19.00%	20.00%
Acute Care Hospital Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 274,393	$ 182,771	$ 549,953	$ 404,762
Percentage of Net Revenue		16.00%	12.00%	16.00%	14.00%
Acute Care Hospital Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 169,705	$ 131,452	$ 281,346	$ 259,411
Percentage of Net Revenue		10.00%	9.00%	8.00%	9.00%
Acute Care Hospital Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 161,261	$ 108,336	$ 296,759	$ 231,791
Percentage of Net Revenue		9.00%	7.00%	9.00%	8.00%
Acute Care Hospital Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 588,806	$ 432,695	$ 1,187,616	$ 973,432
Percentage of Net Revenue		34.00%	29.00%	34.00%	33.00%
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		$ 84,157	$ 78,196	$ 178,407	$ 142,795
Percentage of Net Revenue		5.00%	5.00%	5.00%	5.00%
Acute Care Hospital Services | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 167,898	$ 269,746	$ 311,168	$ 386,029
Percentage of Net Revenue		10.00%	18.00%	9.00%	13.00%
Behavioral Health Services
Disaggregation Of Revenue [Line Items]
Net revenues	[1]	$ 1,431,497	$ 1,259,123	$ 2,746,834	$ 2,565,232
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Behavioral Health Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 92,727	$ 106,571	$ 181,219	$ 226,188
Percentage of Net Revenue		6.00%	8.00%	7.00%	9.00%
Behavioral Health Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 61,532	$ 59,979	$ 119,074	$ 119,217
Percentage of Net Revenue		4.00%	5.00%	4.00%	5.00%
Behavioral Health Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 227,524	$ 154,090	$ 380,664	$ 329,108
Percentage of Net Revenue		16.00%	12.00%	14.00%	13.00%
Behavioral Health Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 334,202	$ 280,865	$ 668,960	$ 583,422
Percentage of Net Revenue		23.00%	22.00%	24.00%	23.00%
Behavioral Health Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 372,146	$ 293,124	$ 720,890	$ 633,811
Percentage of Net Revenue		26.00%	23.00%	26.00%	25.00%
Behavioral Health Services | UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 172,220	$ 136,622	$ 336,886	$ 273,472
Percentage of Net Revenue		12.00%	11.00%	12.00%	11.00%
Behavioral Health Services | Other Patient Revenue and Adjustments, Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 128,944	$ 121,135	$ 249,227	$ 244,195
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		$ 42,202	$ 106,737	$ 89,914	$ 155,819
Percentage of Net Revenue		3.00%	8.00%	3.00%	6.00%
Other
Disaggregation Of Revenue [Line Items]
Net revenues		$ 11,952	$ 3,125	$ 15,060	$ 5,634
Other | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 11,952	$ 3,125	$ 15,060	$ 5,634

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $172 million and $136 million for the three-month periods ended June 30, 2021 and 2020, respectively, and approximately $337 million and $273 million for the six-month periods ended June 30, 2021 and 2020, respectively.  Total assets at our U.K. behavioral health care facilities were approximately $1.369 billion and $1.192 billion as of June 30, 2021 and 2020, respectively.