GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Activity Related to Other Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	$ 1,300
Weighted-average amortization period	1 year 3 months 18 days
Intangible Assets [Roll Forward]
Beginning balance	$ 46,755	$ 44,000	$ 33,200
Additions	3,400	5,200	11,100
Write-off	(1,300)		(300)
Amortization	(2,700)	(2,500)
Ending balance	46,061	46,755	44,000
Noncompete Agreements [Member]
Intangible Assets [Roll Forward]
Beginning balance	4,900	5,900	0
Additions	600	1,500	5,900
Write-off	0		0
Amortization	(2,700)	(2,500)
Ending balance	2,800	4,900	5,900
Certificates of Need and Licenses [Member]
Intangible Assets [Roll Forward]
Beginning balance	24,100	23,900	23,100
Additions	100	200	1,100
Write-off	(500)		(300)
Amortization	0	0
Ending balance	23,700	24,100	23,900
Acquired Names of Business [Member]
Intangible Assets [Roll Forward]
Beginning balance	17,700	14,200	10,100
Additions	2,700	3,500	4,100
Write-off	(800)		0
Amortization	0	0
Ending balance	$ 19,600	$ 17,700	$ 14,200