Schedule of Disaggregates Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 2,687,516	$ 2,612,858
Percentage of Net Revenue	100.00%	100.00%
Medicare
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 485,245	$ 463,030
Percentage of Net Revenue	18.00%	18.00%
Managed Medicare
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 221,952	$ 180,721
Percentage of Net Revenue	8.00%	7.00%
Medicaid
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 283,302	$ 273,606
Percentage of Net Revenue	11.00%	10.00%
Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 342,053	$ 332,197
Percentage of Net Revenue	13.00%	13.00%
Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 855,842	$ 832,604
Percentage of Net Revenue	32.00%	32.00%
UK Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 114,741	$ 100,022
Percentage of Net Revenue	4.00%	4.00%
Other Patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 229,555	$ 248,172
Percentage of Net Revenue	9.00%	9.00%
Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 154,826	$ 182,506
Percentage of Net Revenue	6.00%	7.00%
Acute Care
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 1,445,632	$ 1,389,547
Percentage of Net Revenue	100.00%	100.00%
Acute Care | Medicare
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 342,718	$ 316,385
Percentage of Net Revenue	24.00%	23.00%
Acute Care | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 176,957	$ 144,047
Percentage of Net Revenue	12.00%	10.00%
Acute Care | Medicaid
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 105,966	$ 92,657
Percentage of Net Revenue	7.00%	7.00%
Acute Care | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 111,277	$ 114,552
Percentage of Net Revenue	8.00%	8.00%
Acute Care | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 497,780	$ 477,266
Percentage of Net Revenue	34.00%	34.00%
Acute Care | UK Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 0	$ 0
Percentage of Net Revenue	0.00%	0.00%
Acute Care | Other Patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 112,570	$ 123,374
Percentage of Net Revenue	8.00%	9.00%
Acute Care | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 98,364	$ 121,266
Percentage of Net Revenue	7.00%	9.00%
Other
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 3,888	$ 5,189
Other | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	3,888	5,189
Behavioral Health
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 1,237,996	$ 1,218,122
Percentage of Net Revenue	100.00%	100.00%
Behavioral Health | Medicare
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 142,527	$ 146,645
Percentage of Net Revenue	12.00%	12.00%
Behavioral Health | Managed Medicare
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 44,995	$ 36,674
Percentage of Net Revenue	4.00%	3.00%
Behavioral Health | Medicaid
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 177,336	$ 180,949
Percentage of Net Revenue	14.00%	15.00%
Behavioral Health | Managed Medicaid
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 230,776	$ 217,645
Percentage of Net Revenue	19.00%	18.00%
Behavioral Health | Managed Care (HMO and PPOs)
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 358,062	$ 355,338
Percentage of Net Revenue	29.00%	29.00%
Behavioral Health | UK Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 114,741	$ 100,022
Percentage of Net Revenue	9.00%	8.00%
Behavioral Health | Other Patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 116,985	$ 124,798
Percentage of Net Revenue	9.00%	10.00%
Behavioral Health | Other Non-patient Revenue
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 52,574	$ 56,051
Percentage of Net Revenue	4.00%	5.00%