Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Income Statement [Abstract]
Net sales	$ 356,322		$ 321,140		$ 303,114
Cost of sales	248,059		231,348		232,615
Gross profit	108,263		89,792		70,499
Selling, general and administrative expenses	40,562		33,989		26,261
(Gain) loss on disposal of assets	(305)		(22)		4
Income from operations	68,006		55,825		44,234
Interest income, net	276		221		42
Other (expense) income, net	(36)		248		41
Income before taxes	68,246		56,294		44,317
Income tax provision	24,088		18,747		16,868
Net income	$ 44,158		$ 37,547		$ 27,449
Earnings per share:
Basic (usd per share)	$ 0.81	[1]	$ 0.68	[1]	$ 0.50	[1]
Diluted (usd per share)	$ 0.80	[1]	$ 0.68	[1]	$ 0.49	[1]
Cash dividends declared per common share	$ 0.18	[1]	$ 0.13	[1],[2]	$ 0.16	[1]
Weighted average shares outstanding:
Basic	54,809,319	[1]	55,119,150	[1]	55,237,755	[1]
Diluted	55,369,016	[1]	55,587,381	[1]	55,573,239	[1]

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

[2] Includes special dividend of $0.05 per common share paid on December 24, 2012.