Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net sales	$ 217,294	$ 219,542	$ 418,903	$ 435,883
Cost of goods sold	176,299	166,969	337,382	341,378
Gross profit	40,995	52,573	81,521	94,505
Operating expenses:
Selling, general and administrative	18,667	19,683	36,658	38,656
Research & development expenses	1,063	1,081	2,237	2,096
Total operating expenses	19,730	20,764	38,895	40,752
Operating income	21,265	31,809	42,626	53,753
Interest expense, net	1,403	1,128	2,554	1,833
Foreign exchange loss (gain)	117	(1,042)	2,432	(41)
Income before income taxes	19,745	31,723	37,640	51,961
Provision for income taxes	6,142	11,095	12,094	17,148
Net income	13,603	20,628	25,546	34,813
Net income attributable to participating common shareholders	$ 13,571	$ 20,585	$ 25,500	$ 34,740
Income per participating share:
Basic	$ 0.66	$ 0.94	$ 1.23	$ 1.59
Diluted	$ 0.65	$ 0.93	$ 1.21	$ 1.56
Weighted average participating shares outstanding:
Basic	20,435,846	21,876,265	20,807,777	21,870,343
Diluted	20,722,940	22,251,416	21,109,803	22,243,764
Other comprehensive (loss) income, net of tax:
Change in interest rate swaps, (net of tax ($22), ($236), $245 and ($268))	$ 36	$ (384)	$ (401)	$ (436)
Change in pension and post-retirement plans, (net of tax ($7), ($19), ($108) and $20)	14	(50)	312	72
Other comprehensive (loss) income, net of tax	50	(434)	(89)	(364)
Comprehensive income	$ 13,653	$ 20,194	$ 25,457	$ 34,449