Intangible Assets - Carrying Value and Amortization of Identifiable Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Total identifiable intangible assets, gross carrying amount	$ 509,873		$ 509,873		$ 516,392
Finite-lived intangible assets, accumulated amortization	(94,110)		(94,110)		(78,699)
Total identifiable intangible assets, net carrying amount	415,763		415,763		437,693
Amortized intangible assets:
Amortization expense	6,900	$ 7,900	22,900	$ 22,100
Trademarks
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	5,000		5,000		5,000
Finite-lived intangible assets, accumulated amortization	(5,000)		(5,000)		(4,583)
Finite-lived intangible assets, net carrying amount	0		0		417
Customer relationships
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	287,880		287,880		280,710
Finite-lived intangible assets, accumulated amortization	(81,010)		(81,010)		(61,900)
Finite-lived intangible assets, net carrying amount	206,870		206,870		218,810
Favorable leasehold interests
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	0		0		13,553
Finite-lived intangible assets, accumulated amortization	0		0		(6,064)
Finite-lived intangible assets, net carrying amount	0		0		7,489
Non-compete agreements
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	31,255		31,255		29,400
Finite-lived intangible assets, accumulated amortization	(8,100)		(8,100)		(6,152)
Finite-lived intangible assets, net carrying amount	23,155		23,155		23,248
Trademarks
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Indefinite-lived intangible assets, carrying amount	166,698		$ 166,698		166,698
Amortized intangible assets:
Weighted average time until next renewal			7 years 4 months 24 days
Certificates of need
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Indefinite-lived intangible assets, carrying amount	17,166		$ 17,166		19,174
Accreditations
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Indefinite-lived intangible assets, carrying amount	$ 1,874		$ 1,874		$ 1,857
Amortized intangible assets:
Weighted average time until next renewal			1 year 6 months