Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 2,147,770	$ 1,678,898	$ 1,403,066
Cost of sales	1,654,656	1,249,995	1,097,064
Gross profit	493,114	428,903	306,002
Selling, general and administrative expenses	278,833	228,053	186,032
Severance	0	0	3,716
Operating profit	214,281	200,850	116,254
Interest expense, net	1,437	1,678	1,885
Income before income taxes	212,844	199,172	114,369
Provision for income taxes	79,960	69,501	40,024
Net income	$ 132,884	$ 129,671	$ 74,345
Net income per common share:
Basic (in usd per share)	$ 5.31	$ 5.26	$ 3.06
Diluted (in usd per share)	$ 5.24	$ 5.20	$ 3.02
Weighted average common shares outstanding:
Basic (in shares)	25,020	24,631	24,295
Diluted (in shares)	25,375	24,933	24,650