SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Contract assets and liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Contract assets:
Unbilled receivables	$ 3,412	$ 5,437
Contract liabilities:
Customer advances and unearned income	4,762	4,851
Reserve for audience deficiency	14,583	12,779
Unearned event income	$ 9,037	$ 4,864