REVENUE RECOGNITION - Summary of Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 63,864	$ 66,257
Medicaid
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	25,971	27,532
Medicare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	13,249	15,706
Managed Care
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	9,083	8,126
Private Pay and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 15,561	$ 14,893