ASSETS HELD FOR SALE AND DISCONTINUED OPERATIONS - Major Categories (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Net property and equipment	$ 4,686	$ 48
Radio broadcasting licenses	16,744	10,140
Operating lease right-of-use assets	1,292	0
Operating lease liabilities	(1,315)	0
Net assets held for sale	$ 21,407	$ 10,188