ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	$ 1,341,551	$ 1,269,813
Other comprehensive income (loss) before reclassifications	9,480
Amounts reclassified out of accumulated other comprehensive loss	2,448
Tax benefit	20
Other comprehensive income (loss), net of tax	11,948	(59,306)
Balance ending of period	1,348,450	1,205,805
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	(176,234)
Other comprehensive income (loss) before reclassifications	6,466
Amounts reclassified out of accumulated other comprehensive loss	0
Tax benefit	0
Other comprehensive income (loss), net of tax	6,466
Balance ending of period	(169,768)
Unrealized Gains (Losses) on Available-For-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	135
Other comprehensive income (loss) before reclassifications	(94)
Amounts reclassified out of accumulated other comprehensive loss	0
Tax benefit	20
Other comprehensive income (loss), net of tax	(74)
Balance ending of period	61
Unrealized (Loss) Gain on Interest Rate Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	(33,629)
Other comprehensive income (loss) before reclassifications	3,108
Amounts reclassified out of accumulated other comprehensive loss	2,448
Tax benefit	0
Other comprehensive income (loss), net of tax	5,556
Balance ending of period	(28,073)
Unrealized Loss on Unfunded Pension Liability
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	(1,749)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified out of accumulated other comprehensive loss	0
Tax benefit	0
Other comprehensive income (loss), net of tax	0
Balance ending of period	(1,749)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	(211,477)	(210,051)
Other comprehensive income (loss), net of tax	11,948	(59,306)
Balance ending of period	$ (199,529)	$ (269,357)