ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			$ 615,088
Other comprehensive income	$ 6,920	$ (1,361)	22,410	$ 13,525
Equity, ending balance	700,263		700,263
Tax (benefit)/expense	281	266	785	798
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(118,400)	(110,100)
Other comprehensive income/(loss) before reclassifications			21,600	12,100
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			0	0
Other comprehensive income			21,600	12,100
Equity, ending balance	(96,800)	(98,000)	(96,800)	(98,000)
Pension and Post-Retirement Plan Benefit Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(51,500)	(51,500)
Other comprehensive income/(loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			1,500	1,400
Other comprehensive income			1,500	1,400
Equity, ending balance	(50,000)	(50,100)	(50,000)	(50,100)
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Equity, beginning balance			(169,900)	(161,600)
Other comprehensive income/(loss) before reclassifications			21,600	12,100
Amounts reclassified from accumulated other comprehensive income/(loss) (1)			1,500	1,400
Other comprehensive income			23,100	13,500
Equity, ending balance	$ (146,800)	$ (148,100)	$ (146,800)	$ (148,100)