Commitments and Contingencies - Additional Information (Detail) £ in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2017 GBP (£)	Dec. 31, 2011 USD ($) Hospital	Jan. 31, 2017 USD ($)	Jan. 31, 2017 GBP (£)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability, current	$ 66,000,000	$ 66,000,000					$ 48,000,000
Compensation liability claims	68,000,000	68,000,000					67,000,000
Compensation and related benefits	33,000,000	33,000,000					33,000,000
Accounts receivable, net	1,456,999,000	1,456,999,000					1,439,553,000
Department of Human Services
Commitments and Contingencies Disclosure [Line Items]
Repayment of legal settlement amount on demand				$ 4,000,000
Letters of Credit and Surety Bonds
Commitments and Contingencies Disclosure [Line Items]
Off-balance sheet contingent obligation	122,000,000	122,000,000
Location 1
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible	50,000	50,000
Location 2
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible	250,000	250,000
Illinois
Commitments and Contingencies Disclosure [Line Items]
Accounts receivable, net	49,000,000	49,000,000					38,000,000
Accounts receivable net greater than sixty days Past due	31,000,000	31,000,000					25,000,000
Pennsylvania | Department of Human Services
Commitments and Contingencies Disclosure [Line Items]
Number of behavioral health care hospitals | Hospital				7
Flood | Location 1
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible	500,000	500,000
Professional And General Liability
Commitments and Contingencies Disclosure [Line Items]
Increase in professional and general liability self-insurance reserves relating to prior years	15,000,000	15,000,000
Self Insurance Programs | Letters of Credit and Surety Bonds
Commitments and Contingencies Disclosure [Line Items]
Off-balance sheet contingent obligation	114,000,000	114,000,000
Other Debt Guarantees | Letters of Credit and Surety Bonds
Commitments and Contingencies Disclosure [Line Items]
Off-balance sheet contingent obligation	8,000,000	8,000,000
Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Property insurance | £			£ 1,290
Maximum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	$ 1,000,000,000	$ 1,000,000,000
Percentage of insurance deductible	5.00%	5.00%
Maximum | Earthquake | LAS VEGAS, NEVADA
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	$ 500,000,000	$ 500,000,000
Maximum | Earthquake | CALIFORNIA
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	130,000,000	130,000,000
Maximum | Earthquake | UNITED STATES
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	100,000,000	100,000,000
Maximum | Earthquake | PUERTO RICO
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	40,000,000	40,000,000
Maximum | Earthquake | OTHER STATES
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	$ 250,000,000	$ 250,000,000
Minimum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible	3.00%	3.00%
General and Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability	$ 228,000,000	$ 228,000,000					207,000,000
Subsidiaries | Professional Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £						£ 10
Subsidiaries | Professional Liability | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability					$ 5,000,000		10,000,000
Subsidiaries | General Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £						£ 25
Subsidiaries | General Liability | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability					$ 3,000,000		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%	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	$ 250,000,000	$ 250,000,000	$ 200,000,000
Liability for claims paid under commercially insured coverage	$ 50,000,000	$ 50,000,000