ACCRUED LIABILITIES - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
MGM profit share buyout	$ 0	$ 20,000
Accrued payroll and vacation	6,673	4,860
Other accruals	3,923	4,229
Accrued liabilities	$ 10,596	$ 29,089