REVENUE RECOGNITION - Summary of Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 67,984	$ 66,257
Medicaid
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	27,868	27,532
Medicare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	13,431	15,706
Managed Care
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	9,271	8,126
Private Pay and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 17,414	$ 14,893