ACCUMULATED OTHER COMPREHENSIVE INCOME - Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Accumulated other comprehensive income activity
Balance at the beginning of the period	$ 1,850,389
Other comprehensive (loss) income before reclassifications	(22,865)	$ (21,376)
Amounts reclassified from accumulated other comprehensive income (loss)	1,516	2,068
Net current-period other comprehensive (loss) income	(21,349)	(19,308)
Balance at the end of the period	1,986,282
Accumulated Other Comprehensive Income/(Loss)
Accumulated other comprehensive income activity
Balance at the beginning of the period	(281,709)	(341,948)
Balance at the end of the period	(303,058)	(361,256)
Foreign Currency
Accumulated other comprehensive income activity
Balance at the beginning of the period	(178,025)	(257,124)
Other comprehensive (loss) income before reclassifications	(27,373)	(23,134)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Net current-period other comprehensive (loss) income	(27,373)	(23,134)
Balance at the end of the period	(205,398)	(280,258)
Defined Benefit Pension Plans
Accumulated other comprehensive income activity
Balance at the beginning of the period	(102,322)	(83,147)
Other comprehensive (loss) income before reclassifications	442	0
Amounts reclassified from accumulated other comprehensive income (loss)	4,773	3,076
Net current-period other comprehensive (loss) income	5,215	3,076
Balance at the end of the period	(97,107)	(80,071)
Derivatives
Accumulated other comprehensive income activity
Balance at the beginning of the period	(1,362)	(1,677)
Other comprehensive (loss) income before reclassifications	4,066	1,758
Amounts reclassified from accumulated other comprehensive income (loss)	(3,257)	(1,008)
Net current-period other comprehensive (loss) income	809	750
Balance at the end of the period	$ (553)	$ (927)