CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 48,283	$ 46,320	$ 53,412
Foreign currency translation adjustments	(5,081)	(27,172)	(36,949)
Derivative instruments designated as cash flow hedges:
Unrealized gain (loss) on derivative instruments held at year end (net of taxes of $0 in 2016, $5 in 2015, $50 in 2014)		(2)	(93)
Unrealized gain (loss) reclassified into earnings	11	84	209
Accumulated other comprehensive income (loss) pension and post-retirement benefits:
Actuarial net gain (loss) incurred in fiscal year	1,106	2,760	(20,715)
Amortization of gain (loss)	160	966	3,904
Other comprehensive income (loss)	(3,804)	(23,364)	(53,644)
Comprehensive income (loss)	$ 44,479	$ 22,956	$ (232)