Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Income Statement [Abstract]
Net sales	$ 76,367		$ 66,833
Cost of sales	54,521		51,521
Gross profit	21,846		15,312
Selling, general and administrative expenses	7,629		6,967
(Gain) loss on disposal of assets	(24)		7
Income from operations	14,241		8,338
Interest income, net	69		34
Other expense, net	(21)		(16)
Income before taxes	14,289		8,356
Income tax provision	4,467		1,216
Net income	$ 9,822		$ 7,140
Earnings per share:
Basic (usd per share)	$ 0.27	[1]	$ 0.19	[1]
Diluted (usd per share)	$ 0.26	[1]	$ 0.19	[1]
Cash dividends declared per common share	$ 0		$ 0
Weighted average shares outstanding:
Basic (in shares)	36,694,554	[1]	36,760,632	[1]
Diluted (in shares)	37,075,460	[1]	36,962,144	[1]

[1] Reflects three-for-two stock split effective July 2, 2013