STOCKHOLDERS' EQUITY (Schedule of Stock-Based Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation recorded to (loss) income before income taxes	$ 30,585	$ 30,452	$ 62,335	$ 61,770
Benefit from income taxes	(11,652)	(7,993)	(24,209)	(16,105)
Total stock-based compensation recorded to net (loss) income	18,933	22,459	38,126	45,665
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation recorded to (loss) income before income taxes	943	1,118	1,986	2,361
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation recorded to (loss) income before income taxes	7,302	7,774	14,998	15,461
Product development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation recorded to (loss) income before income taxes	16,827	15,247	34,582	31,322
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation recorded to (loss) income before income taxes	$ 5,513	$ 6,313	$ 10,769	$ 12,626