Intangible Assets - Carrying Value and Amortization of Identifiable Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, accumulated amortization	$ (169,273)		$ (161,206)
Total identifiable intangible assets, gross carrying amount	538,123		536,085
Total identifiable intangible assets, net carrying amount	368,850		374,879
Amortized intangible assets:
Amortization expense	7,600	$ 7,100
Trademarks
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	5,000		5,000
Finite-lived intangible assets, accumulated amortization	(5,000)		(5,000)
Finite-lived intangible assets, net carrying amount	0		0
Customer relationships
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	305,839		304,289
Finite-lived intangible assets, accumulated amortization	(148,283)		(141,111)
Finite-lived intangible assets, net carrying amount	157,556		163,178
Non-compete agreements
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Finite-lived intangible assets, gross carrying amount	37,087		36,746
Finite-lived intangible assets, accumulated amortization	(15,990)		(15,095)
Finite-lived intangible assets, net carrying amount	21,097		21,651
Trademarks
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Indefinite-lived intangible assets	$ 166,698		166,698
Amortized intangible assets:
Weighted average time until next renewal (in years)	7 years 6 months
Certificates of need
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Indefinite-lived intangible assets	$ 21,625		21,478
Accreditations
Finite Lived And Indefinite Lived Intangible Assets By Major Class [Line Items]
Indefinite-lived intangible assets	$ 1,874		$ 1,874
Amortized intangible assets:
Weighted average time until next renewal (in years)	1 year 6 months