Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Consolidated Statements Of Income [Abstract]
Sales	$ 616,904	$ 579,342	$ 1,183,405	$ 1,128,567
Cost of sales	558,317	526,488	1,075,758	1,025,396
Gross profit	58,587	52,854	107,647	103,171
Selling, general and administrative expenses	32,335	28,540	64,986	56,997
Amortization of intangible assets	2,481	2,972	4,962	5,775
Restructuring charges and other costs	1,544	3,602	3,055	6,391
Income from operations	22,227	17,740	34,644	34,008
Interest expense	(2,312)	(2,299)	(4,537)	(4,633)
Interest income	1,213	329	2,287	593
Other income (expense), net	(830)	71	(911)	(152)
Income before income taxes	20,298	15,841	31,483	29,816
Income tax expense	3,122	3,156	4,620	6,079
Net income	$ 17,176	$ 12,685	$ 26,863	$ 23,737
Earnings per share:
Basic	$ 0.35	$ 0.26	$ 0.54	$ 0.48
Diluted	$ 0.34	$ 0.26	$ 0.54	$ 0.47
Weighted-average number of shares outstanding:
Basic	49,766	49,323	49,640	49,586
Diluted	50,239	49,667	50,209	50,042