Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Net sales	$ 85,422	$ 76,768
Cost of sales	59,691	54,970
Gross profit	25,731	21,798
Selling, general and administrative expenses	8,913	8,317
(Gain) loss on disposal of assets	(8)	5
Income from operations	16,826	13,476
Interest income, net	74	44
Other income (expense), net	117	(75)
Income before taxes	17,017	13,445
Income tax provision	6,211	5,046
Net income	$ 10,806	$ 8,399
Earnings per share:
Basic (usd per share)	$ 0.20	$ 0.16
Diluted (usd per share)	0.20	0.15
Cash dividends declared per common share	$ 0	$ 0
Weighted average shares outstanding:
Basic (in shares)	53,061,058	54,083,897
Diluted (in shares)	53,430,103	54,640,389