REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 118,630		$ 354,145
Total revenues, as a percent	100.00%		100.00%
Medicaid
Disaggregation of Revenue [Line Items]
Total revenues	$ 57,191		$ 164,815
Total revenues, as a percent	48.20%		46.50%
Medicare
Disaggregation of Revenue [Line Items]
Total revenues	$ 19,274		$ 59,211
Total revenues, as a percent	16.20%		16.70%
Managed Care
Disaggregation of Revenue [Line Items]
Total revenues	$ 11,794		$ 37,911
Total revenues, as a percent	9.90%		10.70%
Private Pay and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 30,371		$ 92,208
Total revenues, as a percent	25.70%		26.10%
Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Total revenues		$ 119,035		$ 357,406
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		$ 55,910		$ 159,706
Total revenues, as a percent		47.00%		44.70%
Calculated under Revenue Guidance in Effect before Topic 606 | Medicare
Disaggregation of Revenue [Line Items]
Total revenues		$ 20,318		$ 64,713
Total revenues, as a percent		17.10%		18.10%
Calculated under Revenue Guidance in Effect before Topic 606 | Managed Care
Disaggregation of Revenue [Line Items]
Total revenues		$ 11,248		$ 36,748
Total revenues, as a percent		9.40%		10.30%
Calculated under Revenue Guidance in Effect before Topic 606 | Private Pay and other
Disaggregation of Revenue [Line Items]
Total revenues		$ 31,559		$ 96,239
Total revenues, as a percent		26.50%		26.90%