REVENUE RECOGNITION AND ACCOUNTS RECEIVABLE - Summary of Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 49,008	$ 53,691
Medicaid
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	17,254	17,354
Medicare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	9,350	14,273
Managed Care
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	7,861	8,021
Private Pay and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 14,543	$ 14,043