Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 138,389		$ 147,780		$ 146,315		$ 129,845		$ 136,134		$ 142,389		$ 136,109		$ 114,722		$ 562,329	$ 529,354	$ 463,090
Gross profit	41,681		45,115		43,558		36,546		40,628		40,449		37,836		32,549		166,900	151,462	133,437
Operating income	9,831		13,785		11,674		5,990		7,812		10,471		9,976		3,895		41,280	32,154	26,202
Net income	$ 8,902		$ 10,871		$ 8,488		$ 4,273		$ 5,553		$ 8,623		$ 5,841		$ 2,946		$ 32,534	$ 22,963	$ 16,553
Earnings per share:
Basic (in dollars per share)	$ 0.56	[1]	$ 0.69	[1]	$ 0.54	[1]	$ 0.27	[1]	$ 0.36	[1]	$ 0.56	[1]	$ 0.39	[1]	$ 0.20	[1]	$ 2.06	$ 1.51	$ 1.11
Diluted (in dollars per share)	$ 0.55	[1]	$ 0.68	[1]	$ 0.53	[1]	$ 0.26	[1]	$ 0.35	[1]	$ 0.55	[1]	$ 0.38	[1]	$ 0.19	[1]	$ 2.01	$ 1.47	$ 1.10
Shares used in computing earnings per share:
Basic (in shares)	15,831		15,723		15,784		15,787		15,602		15,324		15,098		14,965		15,781	15,248	14,952
Diluted (in shares)	16,204		16,103		16,141		16,163		16,011		15,743		15,419		15,225		16,152	15,601	15,110

[1] The earnings per common share calculations for each of the quarters were based upon the weighted average number of shares and share equivalents outstanding during each period, and the sum of the quarters may not be equal to the full year earnings per share amounts.