REVENUE RECOGNITION AND ACCOUNTS RECEIVABLE - Summary of Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 50,946	$ 53,691
Medicaid
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	18,348	17,354
Medicare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	8,474	14,273
Managed Care
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	7,725	8,021
Private Pay and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 16,399	$ 14,043