REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 329,443	$ 268,505	$ 874,672	$ 741,403
Spot revenues
Disaggregation of Revenue [Line Items]
Net revenues	220,562	183,011	577,561	488,891
Digital revenues
Disaggregation of Revenue [Line Items]
Net revenues	61,378	47,337	169,746	131,188
Network revenues
Disaggregation of Revenue [Line Items]
Net revenues	23,453	18,908	61,626	56,889
Sponsorships and event revenues
Disaggregation of Revenue [Line Items]
Net revenues	12,093	8,776	32,021	32,871
Other revenues
Disaggregation of Revenue [Line Items]
Net revenues	$ 11,957	$ 10,473	$ 33,718	$ 31,564