Condensed Consolidated Statements Of Income (Loss) (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Consolidated Statements Of Income (Loss) [Abstract]
Sales	$ 490,966	$ 601,602	$ 1,005,930	$ 1,204,422
Cost of sales	456,294	552,379	927,897	1,105,162
Gross profit	34,672	49,223	78,033	99,260
Selling, general and administrative expenses	28,516	31,507	60,091	61,514
Amortization of intangible assets	2,371	2,361	4,752	4,728
Restructuring charges and other costs	5,657	3,414	8,572	4,990
Income (loss) from operations	(1,872)	11,941	4,618	28,028
Interest expense	(2,351)	(1,718)	(4,053)	(3,327)
Interest income	287	1,053	886	2,350
Other income (expense), net	32	808	(630)	2,412
Income (loss) before income taxes	(3,904)	12,084	821	29,463
Income tax expense (benefit)	(497)	2,637	376	6,243
Net income	$ (3,407)	$ 9,447	$ 445	$ 23,220
Earnings (loss) per share:
Basic	$ (0.09)	$ 0.25	$ 0.01	$ 0.59
Diluted	$ (0.09)	$ 0.24	$ 0.01	$ 0.58
Weighted-average number of shares outstanding:
Basic	36,439	38,426	36,614	39,522
Diluted	36,439	38,583	36,863	39,843