Schedule of Disaggregates Revenue by Major Source (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Net revenues		$ 2,681,353	$ 2,612,356	$ 5,368,869	$ 5,225,214
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 452,114	$ 433,961	$ 950,398	$ 908,543
Percentage of Net Revenue		17.00%	17.00%	18.00%	17.00%
Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 225,239	$ 193,223	$ 459,332	$ 382,255
Percentage of Net Revenue		8.00%	7.00%	9.00%	7.00%
Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 285,191	$ 303,996	$ 572,306	$ 581,807
Percentage of Net Revenue		11.00%	12.00%	11.00%	11.00%
Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 385,622	$ 343,442	$ 746,337	$ 688,382
Percentage of Net Revenue		14.00%	13.00%	14.00%	13.00%
Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 873,678	$ 834,715	$ 1,747,718	$ 1,681,661
Percentage of Net Revenue		33.00%	32.00%	33.00%	32.00%
UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 119,457	$ 106,390	$ 234,198	$ 206,412
Percentage of Net Revenue		4.00%	4.00%	4.00%	4.00%
Other Patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 185,342	$ 215,037	$ 349,217	$ 412,058
Percentage of Net Revenue		7.00%	8.00%	7.00%	8.00%
Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 154,710	$ 181,592	$ 309,363	$ 364,096
Percentage of Net Revenue		6.00%	7.00%	6.00%	7.00%
Acute Care
Disaggregation Of Revenue [Line Items]
Net revenues		$ 1,403,991	$ 1,366,457	$ 2,849,623	$ 2,756,004
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Acute Care | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 305,471	$ 286,524	$ 661,228	$ 614,461
Percentage of Net Revenue		22.00%	21.00%	23.00%	22.00%
Acute Care | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 174,196	$ 150,510	$ 363,294	$ 302,868
Percentage of Net Revenue		12.00%	11.00%	13.00%	11.00%
Acute Care | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 109,225	$ 121,318	$ 219,004	$ 218,180
Percentage of Net Revenue		8.00%	9.00%	8.00%	8.00%
Acute Care | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 138,346	$ 120,223	$ 268,285	$ 247,518
Percentage of Net Revenue		10.00%	9.00%	9.00%	9.00%
Acute Care | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 512,631	$ 474,876	$ 1,028,609	$ 966,484
Percentage of Net Revenue		37.00%	35.00%	36.00%	35.00%
Acute Care | 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 | Other Patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 63,950	$ 94,826	$ 110,840	$ 167,049
Percentage of Net Revenue		5.00%	7.00%	4.00%	6.00%
Acute Care | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 100,172	$ 118,180	$ 198,363	$ 239,444
Percentage of Net Revenue		7.00%	9.00%	7.00%	9.00%
Behavioral Health
Disaggregation Of Revenue [Line Items]
Net revenues	[1]	$ 1,274,083	$ 1,242,561	$ 2,512,079	$ 2,460,683
Percentage of Net Revenue		100.00%	100.00%	100.00%	100.00%
Behavioral Health | Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 146,643	$ 147,437	$ 289,170	$ 294,082
Percentage of Net Revenue		12.00%	12.00%	12.00%	12.00%
Behavioral Health | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net revenues		$ 51,043	$ 42,713	$ 96,038	$ 79,387
Percentage of Net Revenue		4.00%	3.00%	4.00%	3.00%
Behavioral Health | Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 175,966	$ 182,678	$ 353,302	$ 363,627
Percentage of Net Revenue		14.00%	15.00%	14.00%	15.00%
Behavioral Health | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net revenues		$ 247,276	$ 223,219	$ 478,052	$ 440,864
Percentage of Net Revenue		19.00%	18.00%	19.00%	18.00%
Behavioral Health | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net revenues		$ 361,047	$ 359,839	$ 719,109	$ 715,177
Percentage of Net Revenue		28.00%	29.00%	29.00%	29.00%
Behavioral Health | UK Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 119,457	$ 106,390	$ 234,198	$ 206,412
Percentage of Net Revenue		9.00%	9.00%	9.00%	8.00%
Behavioral Health | Other Patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 121,392	$ 120,211	$ 238,377	$ 245,009
Percentage of Net Revenue		10.00%	10.00%	9.00%	10.00%
Behavioral Health | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 51,259	$ 60,074	$ 103,833	$ 116,125
Percentage of Net Revenue		4.00%	5.00%	4.00%	5.00%
Other
Disaggregation Of Revenue [Line Items]
Net revenues		$ 3,279	$ 3,338	$ 7,167	$ 8,527
Other | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net revenues		$ 3,279	$ 3,338	$ 7,167	$ 8,527

[1] Includes net revenues generated from our behavioral health care facilities located in the U.K. amounting to approximately $119 million and $106 million for the three-month periods ended June 30, 2018 and 2017, respectively, and approximately $234 million and $206 million for the six-month periods ended June 30, 2018 and 2017 respectively. Total assets at our U.K. behavioral health care facilities were approximately $1.123 billion and $1.028 billion as of June 30, 2018 and 2017, respectively.