SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Contract assets and liabilities (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2021	Dec. 31, 2022	Dec. 31, 2021
Contract assets:
Unbilled receivables	$ 5,798	$ 12,597	$ 10,735
Contract liabilities:
Customer advances and unearned income	3,044	6,123	5,503
Reserve for audience deficiency	3,544	9,629	$ 6,020
Unearned event income	$ 5,921	$ 5,708