CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 17,329	$ 20,896	$ 43,465	$ 47,928
Foreign currency translation adjustment	(15,294)	12,591	(8,293)	16,730
Derivative instruments designated as cash flow hedges:
Unrealized gain (loss) on derivative instruments held at period end, net of tax (Note 6)	320	(321)	1,097	(435)
Unrealized loss reclassified into earnings (Note 6)	0	107	0	107
Accumulated other comprehensive loss pension and post-retirement benefits:
Actuarial net gain incurred in fiscal year, net of tax (Note 6)	44	334	87	334
Pension and postretirement benefit plans reclassified into earnings:
Amortization of loss, net of tax (Note 6)	0	6	0	36
Other comprehensive income (loss)	(14,930)	12,717	(7,109)	16,772
Comprehensive income	$ 2,399	$ 33,613	$ 36,356	$ 64,700