ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Contract assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021
Contract assets:
Unbilled receivables	$ 5,798	$ 10,735
Contract liabilities:
Customer advances and unearned income	4,955	7,494
Reserve for audience deficiency	3,544	$ 6,020
Unearned event income	$ 5,921