NET REVENUE AND ACCOUNTS RECEIVABLE - Aging of Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	$ 118,081	$ 114,864
Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	20,012	23,947
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	88,231	82,028
Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	9,838	8,889
0 - 180 days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	93,803	87,229
0 - 180 days | Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	15,121	17,849
0 - 180 days | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	74,369	67,288
0 - 180 days | Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	4,313	2,092
Over 180 days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	24,278	27,635
Over 180 days | Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	4,891	6,098
Over 180 days | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	13,862	14,740
Over 180 days | Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	$ 5,525	$ 6,797