Schedule of Disaggregates Revenue by Major Source (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,912,541	$ 2,822,453	$ 8,471,962	$ 8,482,012
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 439,950	$ 477,291	$ 1,256,473	$ 1,408,964
Percentage of Net Revenue		15.00%	17.00%	15.00%	17.00%
Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 296,787	$ 258,794	$ 820,766	$ 785,968
Percentage of Net Revenue		10.00%	9.00%	10.00%	9.00%
Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 320,427	$ 317,441	$ 908,946	$ 917,112
Percentage of Net Revenue		11.00%	11.00%	11.00%	11.00%
Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 443,662	$ 412,794	$ 1,258,875	$ 1,235,020
Percentage of Net Revenue		15.00%	15.00%	15.00%	15.00%
Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 907,052	$ 878,481	$ 2,514,295	$ 2,709,628
Percentage of Net Revenue		31.00%	31.00%	30.00%	32.00%
UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 155,323	$ 134,905	$ 428,795	$ 415,407
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		$ 183,510	$ 176,882	$ 570,500	$ 515,307
Percentage of Net Revenue		6.00%	6.00%	7.00%	6.00%
Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 165,830	$ 165,865	$ 713,312	$ 494,606
Percentage of Net Revenue		6.00%	6.00%	8.00%	6.00%
Acute Care Hospital Services
Disaggregation Of Revenue [Line Items]
Net revenues		$ 1,610,003	$ 1,528,535	$ 4,598,558	$ 4,575,088
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Acute Care Hospital Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 319,259	$ 333,777	$ 909,594	$ 988,746
Percentage of Net Revenue		20.00%	22.00%	20.00%	22.00%
Acute Care Hospital Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 234,169	$ 197,993	$ 638,931	$ 618,756
Percentage of Net Revenue		15.00%	13.00%	14.00%	14.00%
Acute Care Hospital Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 160,671	$ 148,570	$ 420,082	$ 391,762
Percentage of Net Revenue		10.00%	10.00%	9.00%	9.00%
Acute Care Hospital Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 126,979	$ 133,906	$ 358,770	$ 413,607
Percentage of Net Revenue		8.00%	9.00%	8.00%	9.00%
Acute Care Hospital Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 585,333	$ 554,341	$ 1,558,765	$ 1,690,889
Percentage of Net Revenue		36.00%	36.00%	34.00%	37.00%
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		$ 56,188	$ 45,918	$ 198,983	$ 133,962
Percentage of Net Revenue		3.00%	3.00%	4.00%	3.00%
Acute Care Hospital Services | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 127,404	$ 114,030	$ 513,433	$ 337,366
Percentage of Net Revenue		8.00%	7.00%	11.00%	7.00%
Behavioral Health Services
Disaggregation Of Revenue [Line Items]
Net revenues	[1]	$ 1,299,591	$ 1,291,816	$ 3,864,823	$ 3,898,440
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Behavioral Health Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 120,691	$ 143,514	$ 346,879	$ 420,218
Percentage of Net Revenue		9.00%	11.00%	9.00%	11.00%
Behavioral Health Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 62,618	$ 60,801	$ 181,835	$ 167,212
Percentage of Net Revenue		5.00%	5.00%	5.00%	4.00%
Behavioral Health Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 159,756	$ 168,871	$ 488,864	$ 525,350
Percentage of Net Revenue		12.00%	13.00%	13.00%	13.00%
Behavioral Health Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 316,683	$ 278,888	$ 900,105	$ 821,413
Percentage of Net Revenue		24.00%	22.00%	23.00%	21.00%
Behavioral Health Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 321,719	$ 324,140	$ 955,530	$ 1,018,739
Percentage of Net Revenue		25.00%	25.00%	25.00%	26.00%
Behavioral Health Services | UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 155,323	$ 134,905	$ 428,795	$ 415,407
Percentage of Net Revenue		12.00%	10.00%	11.00%	11.00%
Behavioral Health Services | Other Patient Revenue and Adjustments, Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 127,322	$ 130,964	$ 371,517	$ 381,345
Percentage of Net Revenue		10.00%	10.00%	10.00%	10.00%
Behavioral Health Services | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 35,479	$ 49,733	$ 191,298	$ 148,756
Percentage of Net Revenue		3.00%	4.00%	5.00%	4.00%
Other
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,947	$ 2,102	$ 8,581	$ 8,484
Other | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,947	$ 2,102	$ 8,581	$ 8,484

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $156 million and $135 million for the three-month periods ended September 30, 2020 and 2019, respectively, and approximately $429 million and $415 million for the nine-month periods ended September 30, 2020 and 2019, respectively.  Total assets at our U.K. behavioral health care facilities were approximately $1.257 billion and $1.175 billion as of September 30, 2020 and 2019, respectively.