REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 134,353
Total revenues, as a percent	100.00%
Medicaid
Disaggregation of Revenue [Line Items]
Total revenues	$ 63,531
Total revenues, as a percent	47.30%
Medicare
Disaggregation of Revenue [Line Items]
Total revenues	$ 25,055
Total revenues, as a percent	18.60%
Managed Care
Disaggregation of Revenue [Line Items]
Total revenues	$ 14,175
Total revenues, as a percent	10.60%
Private Pay and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 31,592
Total revenues, as a percent	23.50%
Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Total revenues		$ 141,285
Total revenues, as a percent		100.00%
Calculated under Revenue Guidance in Effect before Topic 606 | Medicaid
Disaggregation of Revenue [Line Items]
Total revenues		$ 63,886
Total revenues, as a percent		45.20%
Calculated under Revenue Guidance in Effect before Topic 606 | Medicare
Disaggregation of Revenue [Line Items]
Total revenues		$ 29,751
Total revenues, as a percent		21.10%
Calculated under Revenue Guidance in Effect before Topic 606 | Managed Care
Disaggregation of Revenue [Line Items]
Total revenues		$ 14,212
Total revenues, as a percent		10.10%
Calculated under Revenue Guidance in Effect before Topic 606 | Private Pay and other
Disaggregation of Revenue [Line Items]
Total revenues		$ 33,436
Total revenues, as a percent		23.60%