Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net sales	$ 219,542	$ 213,176	$ 435,883	$ 427,617
Cost of goods sold	166,969	172,281	341,378	349,688
Gross profit	52,573	40,895	94,505	77,929
Operating expenses:
Selling, general and administrative	19,683	17,939	38,656	36,295
Research & development expenses	1,081	826	2,096	1,579
Total operating expenses	20,764	18,765	40,752	37,874
Operating income	31,809	22,130	53,753	40,055
Interest expense, net	1,128	1,594	1,833	2,746
Foreign exchange (gain) loss	(1,042)	2,915	(41)	2,417
Income before income taxes	31,723	17,621	51,961	34,892
Provision for income taxes	11,095	6,054	17,148	10,922
Net income	20,628	11,567	34,813	23,970
Net income attributable to participating common shareholders	20,585	11,549	34,740	23,932
Income per participating share:
Basic	$ 0.94	$ 0.53	$ 1.59	$ 1.09
Diluted	$ 0.93	$ 0.52	$ 1.56	$ 1.07
Weighted average participating shares outstanding:
Basic	21,876,265	21,925,207	21,870,343	21,925,057
Diluted	22,251,416	22,320,172	22,243,764	22,322,561
Other comprehensive (loss) income, net of tax:
Change in interest rate swaps, (net of tax ($32) and $121)	(384)	1,293	(436)	1,489
Change in pension and post-retirement plans, (net of tax $39 and $85)	(50)	138	(72)	(356)
Other comprehensive (loss) income, net of tax	(434)	1,431	(364)	1,845
Comprehensive income	$ 20,194	$ 12,998	$ 34,449	$ 25,815