Intangible Assets - Carrying Value and Amortization of Identifiable Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Total identifiable intangible assets, Accumulated Amortization	$ (46,500)	$ (27,339)
Total identifiable intangible assets, Gross Carrying Amount	373,019	367,901
Total identifiable intangible assets, Net Carrying Amount	326,519	340,562
Customer relationships
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Identifiable intangibles - Finite lived assets, Gross Carrying Amount	143,953	142,198
Total identifiable intangible assets, Accumulated Amortization	(38,281)	(23,185)
Identifiable intangibles - Finite lived assets, Net Carrying Amount	105,672	119,013
Favorable leasehold interests
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Identifiable intangibles - Finite lived assets, Gross Carrying Amount	13,295	13,089
Total identifiable intangible assets, Accumulated Amortization	(4,319)	(2,317)
Identifiable intangibles - Finite lived assets, Net Carrying Amount	8,976	10,772
Non-compete agreements
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Identifiable intangibles - Finite lived assets, Gross Carrying Amount	28,023	26,655
Total identifiable intangible assets, Accumulated Amortization	(3,900)	(1,837)
Identifiable intangibles - Finite lived assets, Net Carrying Amount	24,123	24,818
Customer relationships and non-compete agreements
Amortized intangible assets:
Amortization expense	17,400	16,300	$ 8,900
Estimated amortization expense
2018	16,831
2019	16,802
2020	16,647
2021	16,483
2022	16,332
Trademarks
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Identifiable intangibles - Indefinite lived assets	$ 166,698	166,698
Amortized intangible assets:
Weighted average time until next renewal	1 year 10 months 24 days
Certificates of need
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Identifiable intangibles - Indefinite lived assets	$ 19,155	17,026
Accreditations
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Identifiable intangibles - Indefinite lived assets	$ 1,895	$ 2,235
Amortized intangible assets:
Weighted average time until next renewal	1 year 6 months