Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Net sales	$ 341,802	$ 288,332
Cost of sales	219,833	186,255
Selling and administrative expenses	66,221	60,550
Total operating costs and expenses	286,054	246,805
Operating income	55,748	41,527
Interest expense	3,349	2,991
Other expense (income), net	23	227
Income before income taxes	52,376	38,309
Income taxes	14,073	9,461
Net income	$ 38,303	$ 28,848
Per common share:
Basic (in dollars per share)	$ 0.71	$ 0.53
Diluted (in dollars per share)	0.70	0.53
Dividends (in dollars per share)	$ 0.13	$ 0.12
Weighted average common shares outstanding:
Basic (in shares)	54,179,130	54,245,728
Diluted (in shares)	54,651,835	54,672,773