ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			$ 702,621
Other comprehensive income	$ (32,138)	$ 6,596	(24,542)	$ 15,490
Equity, ending balance	715,024		715,024
Income tax expense related to items of other comprehensive income	176	252	353	504
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(99,700)	(118,400)
Other comprehensive income/(loss) before reclassifications			(25,800)	15,200
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			0	0
Other comprehensive income			(25,800)	15,200
Equity, ending balance	(125,500)	(103,200)	(125,500)	(103,200)
Pension and Post-Retirement Plan Benefit Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(49,300)	(51,500)
Other comprehensive income/(loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			1,200	1,000
Other comprehensive income			1,200	1,000
Equity, ending balance	(48,100)	(50,500)	(48,100)	(50,500)
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(149,000)	(169,900)
Other comprehensive income/(loss) before reclassifications			(25,800)	15,200
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			1,200	1,000
Other comprehensive income			(24,600)	16,200
Equity, ending balance	$ (173,600)	$ (153,700)	$ (173,600)	$ (153,700)