Commitments and Contingencies - Schedule of Changes in General and Professional Liability and Workers Compensation Reserves (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Line Items]
Beginning balance	$ 274,815	$ 271,476	$ 259,718
Liabilities assumed in acquisition		661
Plus: Accrued insurance expense, net of commercial premiums paid	102,595	84,638	90,895
Less: Payments made in settlement of self-insured claims	(79,188)	(81,960)	(79,137)
Ending balance	298,222	274,815	271,476
General and Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Beginning balance	207,459	203,973	192,904
Liabilities assumed in acquisition		0
Plus: Accrued insurance expense, net of commercial premiums paid	65,049	54,671	58,460
Less: Payments made in settlement of self-insured claims	(43,817)	(51,185)	(47,391)
Ending balance	228,691	207,459	203,973
Workers’ Compensation
Commitments and Contingencies Disclosure [Line Items]
Beginning balance	67,356	67,503	66,814
Liabilities assumed in acquisition		661
Plus: Accrued insurance expense, net of commercial premiums paid	37,546	29,967	32,435
Less: Payments made in settlement of self-insured claims	(35,371)	(30,775)	(31,746)
Ending balance	$ 69,531	$ 67,356	$ 67,503