GOODWILL AND OTHER INTANGIBLE ASSETS - Carrying Amount and Accumulated Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Total gross intangible assets	$ 543,618		$ 543,618		$ 530,955
Total accumulated amortization	(168,089)		(168,089)		(164,935)
Total intangible assets, net	375,529		375,529		366,020
Amortization expense for intangible assets	8,700	$ 9,000	16,200	$ 17,600
Referral sources
Finite-Lived Intangible Assets [Line Items]
Total gross intangible assets	504,812		504,812		482,200
Total accumulated amortization	(152,444)		(152,444)		(137,613)
Trademarks/names
Finite-Lived Intangible Assets [Line Items]
Total gross intangible assets	38,172		38,172		47,718
Total accumulated amortization	(15,611)		(15,611)		(26,936)
Other amortizable intangible assets
Finite-Lived Intangible Assets [Line Items]
Total gross intangible assets	634		634		1,037
Total accumulated amortization	$ (34)		$ (34)		$ (386)