Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements Of Income [Abstract]
Sales	$ 2,466,811	$ 2,310,415	$ 2,540,873
Cost of sales	2,239,114	2,096,952	2,321,619
Gross profit	227,697	213,463	219,254
Selling, general and administrative expenses	130,401	113,448	107,462
Amortization of intangible assets	10,065	11,838	4,962
Restructuring charges and other costs	8,628	12,539	13,861
Income from operations	78,603	75,638	92,969
Interest expense	(9,405)	(9,304)	(2,996)
Interest income	5,370	2,136	1,207
Other expense	(1,786)	(282)	(1,141)
Income before income taxes	72,782	68,188	90,039
Income tax expense (benefit)	104,747	4,141	(5,362)
Net income (loss)	$ (31,965)	$ 64,047	$ 95,401
Earnings (loss) per share:
Basic	$ (0.64)	$ 1.3	$ 1.85
Diluted	$ (0.64)	$ 1.29	$ 1.83
Weighted-average number of shares outstanding:
Basic	49,680	49,298	51,573
Diluted	49,680	49,825	52,088