Commitments and Contingencies - Additional Information (Detail) £ in Millions	1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended			12 Months Ended						66 Months Ended
	Jul. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 GBP (£)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Sep. 30, 2019 USD ($)	Jan. 31, 2017 USD ($)	Jan. 31, 2017 GBP (£)	Dec. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability, current		$ 42,000,000				$ 42,000,000			$ 42,000,000						$ 42,000,000
Compensation liability claims		75,000,000				75,000,000			72,000,000						75,000,000
Compensation and related benefits		40,000,000				40,000,000			40,000,000						40,000,000
Accounts receivable, net		1,544,077,000				1,544,077,000			1,509,909,000						1,544,077,000
Provision for income tax related to non-deductible DOJ reserve		6,000,000				6,000,000
Department of Human Services
Commitments and Contingencies Disclosure [Line Items]
Repayment of legal settlement amount on demand										$ 4,000,000	$ 4,000,000	$ 4,000,000	$ 4,000,000	$ 4,000,000
Amount claimed from over payments of legal settlements										5,000,000	7,000,000	7,000,000	$ 4,000,000
Amount claimed from over payments of legal settlements due to change in calculations												2,000,000
DOJ
Commitments and Contingencies Disclosure [Line Items]
Definitive settlement and related civil agreements	$ 127,000,000
Increase in aggregate pre-tax reserve				$ 48,000,000		134,000,000		$ 70,000,000	123,000,000
Pre-tax increase to reserve for civil aspects						11,000,000
DOJ | Federal and State Income Taxes
Commitments and Contingencies Disclosure [Line Items]
Provision for income tax related to non-deductible DOJ reserve			$ 6,000,000		$ 6,000,000
River Point Behavioral Health
Commitments and Contingencies Disclosure [Line Items]
Amount withheld in contingent Medicare payment suspension															8,600,000
Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Minimum Insurance Deductible		50,000				50,000									50,000
Maximum insurance deductible		250,000				250,000									250,000
Flood
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible		500,000				500,000									500,000
Illinois
Commitments and Contingencies Disclosure [Line Items]
Accounts receivable, net		29,000,000				29,000,000			32,000,000						29,000,000
Accounts receivable net greater than sixty days Past due		13,000,000				13,000,000			18,000,000						13,000,000
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									$ 1,000,000,000
Percentage of insurance deductible		5.00%				5.00%									5.00%
Maximum | Flood
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		$ 100,000,000				$ 100,000,000									$ 100,000,000
Maximum | LAS VEGAS, NEVADA | Earthquake
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		500,000,000				500,000,000									500,000,000
Maximum | CALIFORNIA | Earthquake
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		130,000,000				130,000,000									130,000,000
Maximum | Faulty Zones of UNITED STATES | Earthquake
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		100,000,000				100,000,000									100,000,000
Maximum | PUERTO RICO | Earthquake
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		40,000,000				40,000,000									40,000,000
Maximum | PUERTO RICO | Flood
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		1,000,000				1,000,000									1,000,000
Maximum | OTHER STATES | Earthquake
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		250,000,000				250,000,000									250,000,000
Maximum | Texas | Flood
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		$ 10,000,000				$ 10,000,000									$ 10,000,000
Minimum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible		3.00%				3.00%									3.00%
General and Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability		$ 248,000,000				$ 248,000,000			$ 243,000,000						$ 248,000,000
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%									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	$ 200,000,000						$ 250,000,000
Liability for claims paid under commercially insured coverage		$ 5,000,000				$ 5,000,000									$ 5,000,000
Subsidiaries | General And Professional Liability Insurance Policies | Maximum | Located in U.K.
Commitments and Contingencies Disclosure [Line Items]
Liability for claims paid under commercially insured coverage		$ 8,500,000				$ 8,500,000									$ 8,500,000