Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Income Statement [Abstract]
Net sales	$ 102,917		$ 89,690		$ 271,594		$ 247,764
Cost of sales	69,567		63,074		188,522		178,160
Gross profit	33,350		26,616		83,072		69,604
Selling, general and administrative expenses	13,830		9,687		32,043		25,743
Gain on disposal of assets	0		0		(24)		(52)
Income from operations	19,520		16,929		51,053		43,913
Interest income, net	55		60		195		151
Other income (expense), net	(43)		15		(30)		252
Income before taxes	19,532		17,004		51,218		44,316
Income tax provision	7,092		6,482		17,593		14,535
Net income	$ 12,440		$ 10,522		$ 33,625		$ 29,781
Earnings per share:
Basic (usd per share)	$ 0.23	[1]	$ 0.19	[1]	$ 0.61	[1]	$ 0.54	[1]
Diluted (usd per share)	$ 0.22	[1]	$ 0.19	[1]	$ 0.61	[1]	$ 0.54	[1]
Cash dividends declared per common share	$ 0	[1]	$ 0	[1]	$ 0.09	[1]	$ 0.07	[1]
Weighted average shares outstanding:
Basic (in shares)	54,905,288	[1]	55,113,393	[1]	54,851,911	[1]	55,128,986	[1]
Diluted (in shares)	55,484,043	[1]	55,526,342	[1]	55,423,294	[1]	55,562,663	[1]

[1] Reflects three-for-two stock split effective July 16, 2014