Condensed Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Net sales	$ 1,678,898	$ 1,403,066	$ 1,190,782
Cost of sales	1,249,995	1,097,064	935,859
Gross profit	428,903	306,002	254,923
Selling, general and administrative expenses	228,053	186,032	157,482
Severance	0	3,716	0
Sale of extrusion assets	0	0	1,954
Operating profit	200,850	116,254	95,487
Interest expense, net	1,678	1,885	430
Income before income taxes	199,172	114,369	95,057
Provision for income taxes	69,501	40,024	32,791
Net income	$ 129,671	$ 74,345	$ 62,266
Net income per common share:
Basic (in usd per share)	$ 5.26	$ 3.06	$ 2.60
Diluted (in usd per share)	$ 5.20	$ 3.02	$ 2.56
Weighted average common shares outstanding:
Basic (in shares)	24,631	24,295	23,911
Diluted (in shares)	24,933	24,650	24,334