Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed Consolidated Statements Of Income (Loss) [Abstract]
Net sales	$ 601,602	$ 660,591	$ 1,204,422	$ 1,268,727
Cost of sales	548,604	606,292	1,097,624	1,156,110
Gross profit	52,998	54,299	106,798	112,617
Selling, general and administrative expenses	35,282	35,825	69,052	71,575
Amortization of intangible assets	2,361	2,367	4,728	4,733
Restructuring charges and other costs	3,414	1,758	4,990	3,993
Income from operations	11,941	14,349	28,028	32,316
Interest expense	(1,718)	(2,293)	(3,327)	(4,721)
Interest income	1,053	1,645	2,350	3,578
Other income (expense)	808	(355)	2,412	(312)
Income before income taxes	12,084	13,346	29,463	30,861
Income tax expense	2,637	2,403	6,243	43,559
Net income (loss)	$ 9,447	$ 10,943	$ 23,220	$ (12,698)
Earnings (loss) per share:
Basic	$ 0.25	$ 0.23	$ 0.59	$ (0.26)
Diluted	$ 0.24	$ 0.23	$ 0.58	$ (0.26)
Weighted-average number of shares outstanding:
Basic	38,426	47,451	39,522	47,981
Diluted	38,583	47,631	39,843	47,981