ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Summary (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Loss
Balance at beginning of period	$ 1,312,941
Other comprehensive income (loss) before reclassifications	1,670	$ 3,853
Amounts reclassified to earnings		139
Net current period other comprehensive income		3,992
Balance at end of period	1,322,858
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Loss
Balance at beginning of period	(1,861)	2,232
Balance at end of period	(191)	6,224
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Loss
Balance at beginning of period	(1,864)	2,232
Other comprehensive income (loss) before reclassifications	1,673	3,853
Amounts reclassified to earnings		139
Net current period other comprehensive income		3,992
Balance at end of period	(191)	$ 6,224
Unrealized Gains (Losses) On Available-For-Sale Debt Securities
Accumulated Other Comprehensive Loss
Balance at beginning of period	3
Other comprehensive income (loss) before reclassifications	(3)
Balance at end of period	$ 0