STOCK-BASED COMPENSATION (Summary of stock-based compensation expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 116,889	$ 48,785	$ 45,582
Total unrecognized compensation cost	$ 84,300
Amortization period of unrecognized compensation cost	1 year 7 months 6 days
Ticketmaster Plan [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Expiration period	10 years
Selling, General and Administrative Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 88,620	21,947	18,621
Corporate expenses [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 28,269	$ 26,838	$ 26,961