GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Activity Related to Other Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	$ 4,200	$ 1,500
Intangible assets, accumulated amortization	22,973	7,044
Intangible Assets [Roll Forward]
Beginning balance	64,748	44,100
Additions	30,300	28,900
Write-off	(4,200)	(1,500)
Amortization	(16,600)	(6,800)
Ending balance	74,183	64,748
Amortizable acquired names [Member]
Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	$ 0	0
Weighted-average amortization period	1 year 3 months 18 days
Intangible Assets [Roll Forward]
Beginning balance	$ 5,600	0
Additions	7,000	10,000
Write-off	0	0
Amortization	(7,100)	(4,400)
Ending balance	5,500	5,600
Noncompete Agreements [Member]
Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	0	0
Intangible assets, accumulated amortization	$ 700
Weighted-average amortization period	1 year 2 months 12 days
Intangible Assets [Roll Forward]
Beginning balance	$ 3,400	600
Additions	11,500	5,200
Write-off	0	0
Amortization	(7,100)	(2,400)
Ending balance	7,800	3,400
Certificates of Need and Licenses [Member]
Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	0	0
Intangible Assets [Roll Forward]
Beginning balance	37,600	23,900
Additions	11,800	13,700
Write-off	0	0
Amortization	(2,400)	0
Ending balance	47,000	37,600
Unamortizable acquired names [Member]
Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	4,200	1,500
Intangible Assets [Roll Forward]
Beginning balance	18,100	19,600
Additions	0	0
Write-off	(4,200)	(1,500)
Amortization	0	0
Ending balance	$ 13,900	$ 18,100