Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Consolidated Statements Of Income [Abstract]
Sales	$ 603,550	$ 574,341	$ 1,786,955	$ 1,702,908
Cost of sales	545,395	521,519	1,621,153	1,546,915
Gross profit	58,155	52,822	165,802	155,993
Selling, general and administrative expenses	32,093	28,085	97,079	85,082
Amortization of intangible assets	2,736	3,170	7,698	8,945
Restructuring charges and other costs	2,511	3,485	5,566	9,876
Income from operations	20,815	18,082	55,459	52,090
Interest expense	(2,324)	(2,302)	(6,861)	(6,935)
Interest income	1,334	577	3,621	1,170
Other expense, net	(394)	(383)	(1,305)	(535)
Income before income taxes	19,431	15,974	50,914	45,790
Income tax expense (benefit)	1,919	(5,768)	6,539	311
Net income	$ 17,512	$ 21,742	$ 44,375	$ 45,479
Earnings per share:
Basic	$ 0.35	$ 0.44	$ 0.89	$ 0.92
Diluted	$ 0.35	$ 0.44	$ 0.88	$ 0.91
Weighted-average number of shares outstanding:
Basic	49,865	48,965	49,716	49,377
Diluted	50,330	49,414	50,292	49,878