CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 19,734	$ 25,532	$ 63,199	$ 73,460
Foreign currency translation adjustment	(1,608)	6,407	(9,901)	23,136
Derivative instruments designated as cash flow hedges:
Unrealized gain (loss) on derivative instruments held at period end, net of tax (Note 6)	211	(51)	1,308	(487)
Unrealized loss reclassified into earnings (Note 6)	0	115	0	222
Accumulated other comprehensive loss pension and post-retirement benefits:
Actuarial net gain (loss) incurred in fiscal year, net of tax (Note 6)	0	(300)	0	35
Pension and postretirement benefit plans reclassified into earnings:
Amortization of loss, net of tax (Note 6)	44	0	131	36
Other comprehensive income (loss)	(1,353)	6,171	(8,462)	22,942
Comprehensive income	$ 18,381	$ 31,703	$ 54,737	$ 96,402