RELATED-PARTY TRANSACTIONS - Summary of Balance Sheet Assets and Liabilities from Related Parties (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Intangibles, net	$ 1,350	$ 1,624
MGM \| Marketing Agreement
Related Party Transaction [Line Items]
Intangibles, net	$ 1,000	1,000
Accrued liabilities		$ 20,000

Carrying amount as of the balance sheet date of obligations due all related parties.

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+ Details