Commitments and Contingencies - Additional Information (Detail) £ in Millions	1 Months Ended		9 Months Ended
	Aug. 31, 2015	Nov. 30, 2010 USD ($) Facility	Sep. 30, 2015 GBP (£)	Oct. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Oct. 31, 2012 USD ($)	Nov. 30, 2010 GBP (£)
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability					$ 210,000,000	$ 193,000,000
Self-insured for professional and general liability, current					51,000,000	51,000,000
Compensation liability claims					70,000,000	67,000,000
Compensation and related benefits					32,000,000	32,000,000
Accounts receivable, net					1,328,300,000	1,282,735,000
Payment suspension period increased	180 days
Letters of Credit and Surety Bonds
Commitments and Contingencies Disclosure [Line Items]
Off-balance sheet contingent obligation					125,000,000
Self Insurance Programs | Letters of Credit and Surety Bonds
Commitments and Contingencies Disclosure [Line Items]
Off-balance sheet contingent obligation					96,000,000
Other Debt Guarantees | Letters of Credit and Surety Bonds
Commitments and Contingencies Disclosure [Line Items]
Off-balance sheet contingent obligation					29,000,000
Location 1
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible					50,000
Location 2
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible					250,000
Illinois
Commitments and Contingencies Disclosure [Line Items]
Accounts receivable, net					24,000,000	44,000,000
Accounts receivable net greater than sixty days Past due					8,000,000	23,000,000
Accounts receivable					83,000,000	$ 102,000,000
Illinois | Subsequent Event
Commitments and Contingencies Disclosure [Line Items]
Accounts receivable				$ 31,000,000
Illinois | Uncompensated Care Program Revenues
Commitments and Contingencies Disclosure [Line Items]
Accounts receivable					63,000,000
Illinois | Delivery System Reform Incentive Pool
Commitments and Contingencies Disclosure [Line Items]
Accounts receivable					20,000,000
Earthquake
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible					250,000
Earthquake | PUERTO RICO
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses					25,000,000
Maximum insurance deductible					25,000
Flood | Location 1
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible					500,000
Flood | Location 2
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible					250,000
Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Number of inpatient behavioral health hospitals | Facility		21
Property insurance | £			£ 180
Maximum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses					$ 1,000,000,000
Percentage of insurance deductible					5.00%
Maximum | Earthquake
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses					$ 250,000,000
Maximum | Earthquake | UNITED STATES
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses					$ 100,000,000
Percentage of insurance deductible					5.00%
Minimum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible					3.00%
Minimum | Earthquake | UNITED STATES
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible					1.00%
Professional Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £									£ 10
General Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £									£ 25
Subsidiaries | Professional Liability | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability		$ 10,000,000
Subsidiaries | General Liability | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability		$ 3,000,000
Subsidiaries | General and Professional Liability Insurance Policies
Commitments and Contingencies Disclosure [Line Items]
Percentage of liability for claims paid under commercially insured coverage					10.00%
Subsidiaries | General and Professional Liability Insurance Policies | Maximum
Commitments and Contingencies Disclosure [Line Items]
Purchased several excess policies through commercial insurance carriers per occurrence					$ 250,000,000		$ 200,000,000
Liability for claims paid under commercially insured coverage					60,000,000
Subsidiaries | General and Professional Liability Insurance Policies | Minimum
Commitments and Contingencies Disclosure [Line Items]
Liability for claims paid under commercially insured coverage					10,000,000
Psychiatric Solutions Inc | General and Professional Liability Insurance Policies | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability					$ 3,000,000
Behavioral Health Facilities Acquired from Ascend Health Corporation | General and Professional Liability Insurance Policies
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible								$ 100,000
Behavioral Health Facilities Acquired from Ascend Health Corporation | General and Professional Liability Insurance Policies | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability								$ 12,000,000