ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			$ 735,827
Other comprehensive income/(loss)	$ 1,870	$ (32,138)	(431)	$ (24,542)
Equity, ending balance	760,902		760,902
Income tax expense related to items of other comprehensive income/(loss)	141	176	282	353
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(134,500)	(99,700)
Other comprehensive income/(loss) before reclassifications			(1,400)	(25,800)
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			0	0
Other comprehensive income/(loss)			(1,400)	(25,800)
Equity, ending balance	(135,900)	(125,500)	(135,900)	(125,500)
Pension and Post-Retirement Plan Benefit Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(48,500)	(49,300)
Other comprehensive income/(loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			900	1,200
Other comprehensive income/(loss)			900	1,200
Equity, ending balance	(47,600)	(48,100)	(47,600)	(48,100)
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(183,000)	(149,000)
Other comprehensive income/(loss) before reclassifications			(1,400)	(25,800)
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			900	1,200
Other comprehensive income/(loss)			(500)	(24,600)
Equity, ending balance	$ (183,500)	$ (173,600)	$ (183,500)	$ (173,600)