Schedule of Disaggregates Revenue by Major Source (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,822,453	$ 2,648,913	$ 8,482,012	$ 8,017,782
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 477,291	$ 451,333	$ 1,408,964	$ 1,416,885
Percentage of Net Revenue		17.00%	17.00%	17.00%	18.00%
Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 258,794	$ 230,533	$ 785,968	$ 702,006
Percentage of Net Revenue		9.00%	9.00%	9.00%	9.00%
Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 317,441	$ 296,591	$ 917,112	$ 872,710
Percentage of Net Revenue		11.00%	11.00%	11.00%	11.00%
Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 412,794	$ 365,529	$ 1,235,020	$ 1,130,528
Percentage of Net Revenue		15.00%	14.00%	15.00%	14.00%
Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 878,481	$ 834,273	$ 2,709,628	$ 2,600,190
Percentage of Net Revenue		31.00%	31.00%	32.00%	32.00%
UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 134,905	$ 129,965	$ 415,407	$ 364,163
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		$ 176,882	$ 188,212	$ 515,307	$ 469,460
Percentage of Net Revenue		6.00%	7.00%	6.00%	6.00%
Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 165,865	$ 152,477	$ 494,606	$ 461,840
Percentage of Net Revenue		6.00%	6.00%	6.00%	6.00%
Acute Care Hospital Services
Disaggregation Of Revenue [Line Items]
Net revenues		$ 1,528,535	$ 1,383,050	$ 4,575,088	$ 4,232,673
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Acute Care Hospital Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 333,777	$ 295,691	$ 988,746	$ 972,073
Percentage of Net Revenue		22.00%	21.00%	22.00%	23.00%
Acute Care Hospital Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 197,993	$ 175,248	$ 618,756	$ 550,683
Percentage of Net Revenue		13.00%	13.00%	14.00%	13.00%
Acute Care Hospital Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 148,570	$ 126,977	$ 391,762	$ 349,794
Percentage of Net Revenue		10.00%	9.00%	9.00%	8.00%
Acute Care Hospital Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 133,906	$ 123,296	$ 413,607	$ 410,243
Percentage of Net Revenue		9.00%	9.00%	9.00%	10.00%
Acute Care Hospital Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 554,341	$ 500,688	$ 1,690,889	$ 1,547,496
Percentage of Net Revenue		36.00%	36.00%	37.00%	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		$ 45,918	$ 62,055	$ 133,962	$ 104,926
Percentage of Net Revenue		3.00%	4.00%	3.00%	2.00%
Acute Care Hospital Services | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 114,030	$ 99,095	$ 337,366	$ 297,458
Percentage of Net Revenue		7.00%	7.00%	7.00%	7.00%
Behavioral Health Services
Disaggregation Of Revenue [Line Items]
Net revenues	[1]	$ 1,291,816	$ 1,262,472	$ 3,898,440	$ 3,774,551
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Behavioral Health Services | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 143,514	$ 155,642	$ 420,218	$ 444,812
Percentage of Net Revenue		11.00%	12.00%	11.00%	12.00%
Behavioral Health Services | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 60,801	$ 55,285	$ 167,212	$ 151,323
Percentage of Net Revenue		5.00%	4.00%	4.00%	4.00%
Behavioral Health Services | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 168,871	$ 169,614	$ 525,350	$ 522,916
Percentage of Net Revenue		13.00%	13.00%	13.00%	14.00%
Behavioral Health Services | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 278,888	$ 242,233	$ 821,413	$ 720,285
Percentage of Net Revenue		22.00%	19.00%	21.00%	19.00%
Behavioral Health Services | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 324,140	$ 333,585	$ 1,018,739	$ 1,052,694
Percentage of Net Revenue		25.00%	26.00%	26.00%	28.00%
Behavioral Health Services | UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 134,905	$ 129,965	$ 415,407	$ 364,163
Percentage of Net Revenue		10.00%	10.00%	11.00%	10.00%
Behavioral Health Services | Other Patient Revenue and Adjustments,Net
Disaggregation Of Revenue [Line Items]
Net revenues		$ 130,964	$ 126,157	$ 381,345	$ 364,534
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		$ 49,733	$ 49,991	$ 148,756	$ 153,824
Percentage of Net Revenue		4.00%	4.00%	4.00%	4.00%
Other
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,102	$ 3,391	$ 8,484	$ 10,558
Other | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,102	$ 3,391	$ 8,484	$ 10,558

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $135 million and $130 million for the three-month periods ended September 30, 2019 and 2018, respectively, and approximately $415 million and $364 million for the nine-month periods ended September 30, 2019 and 2018, respectively.  Total assets at our U.K. behavioral health care facilities were approximately $1.175 billion and $1.231 billion as of September 30, 2019 and 2018, respectively.