Quarterly Results of Operations (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Unaudited quarterly results of operations
Net sales	$ 80,155	$ 86,586	$ 98,824	$ 104,519	$ 96,319	$ 101,143	$ 115,922	$ 111,307
Income from operations	1,846	5,917	8,275	9,033	5,169	5,795	9,251	9,217	25,071	29,432	16,248
Net income	$ 8,206	$ 3,115	$ 7,038	$ 5,909	$ 4,901	$ 4,702	$ 5,827	$ 5,507	$ 24,268	$ 20,937	$ 6,416
Basic net income per share	$ 0.48	$ 0.18	$ 0.41	$ 0.35	$ 0.29	$ 0.28	$ 0.35	$ 0.33	$ 1.43	$ 1.24	$ 0.39
Diluted net income per share	$ 0.48	$ 0.18	$ 0.41	$ 0.35	$ 0.29	$ 0.28	$ 0.34	$ 0.33	$ 1.42	$ 1.24	$ 0.39
Weighted average shares outstanding:
Basic number of shares	17,044	17,044	17,026	16,961	16,949	16,949	16,864	16,664	17,009	16,817	16,455
Effect of dilutive stock options	106	106	113	114	108	112	255	246	105	136	115
Diluted number of shares	17,150	17,150	17,139	17,075	17,057	17,061	17,119	16,910	17,114	16,953	16,570