REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 135,370		$ 269,723
Total revenues, as a percent	100.00%		100.00%
Medicaid
Disaggregation of Revenue [Line Items]
Total revenues	$ 64,284		$ 127,815
Total revenues, as a percent	47.50%		47.40%
Medicare
Disaggregation of Revenue [Line Items]
Total revenues	$ 24,291		$ 49,346
Total revenues, as a percent	17.90%		18.30%
Managed Care
Disaggregation of Revenue [Line Items]
Total revenues	$ 14,161		$ 28,336
Total revenues, as a percent	10.50%		10.50%
Private Pay and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 32,634		$ 64,226
Total revenues, as a percent	24.10%		23.80%
Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Total revenues		$ 141,082		$ 282,367
Total revenues, as a percent		100.00%		100.00%
Calculated under Revenue Guidance in Effect before Topic 606 | Medicaid
Disaggregation of Revenue [Line Items]
Total revenues		$ 65,603		$ 129,489
Total revenues, as a percent		46.50%		45.90%
Calculated under Revenue Guidance in Effect before Topic 606 | Medicare
Disaggregation of Revenue [Line Items]
Total revenues		$ 27,863		$ 57,614
Total revenues, as a percent		19.70%		20.40%
Calculated under Revenue Guidance in Effect before Topic 606 | Managed Care
Disaggregation of Revenue [Line Items]
Total revenues		$ 13,303		$ 27,515
Total revenues, as a percent		9.40%		9.70%
Calculated under Revenue Guidance in Effect before Topic 606 | Private Pay and other
Disaggregation of Revenue [Line Items]
Total revenues		$ 34,313		$ 67,749
Total revenues, as a percent		24.40%		24.00%