Quarterly Information - 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
Quarterly Information [Abstract]
Net sales	$ 77,154	$ 72,190	$ 69,956	$ 73,605	$ 86,514	$ 74,263	$ 94,971	$ 89,068	$ 292,905	$ 344,816	$ 326,886
Gross profit	17,852	16,124	15,654	17,369	19,527	16,204	27,381	25,674
Net income	3,319	1,528	1,508	2,000	1,754	2,756	9,123	7,676	8,355	21,309	15,456
Net income per common share:
Basic	$ 0.32	$ 0.15	$ 0.15	$ 0.19	$ 0.17	$ 0.27	$ 0.88	$ 0.74	$ 0.81	$ 2.07	$ 1.51
Diluted	$ 0.32	$ 0.15	$ 0.15	$ 0.19	$ 0.17	$ 0.26	$ 0.88	$ 0.74	$ 0.80	$ 2.05	$ 1.50
Comprehensive income	$ (5,815)	$ 4,362	$ 1,278	$ 5,445	$ (18,995)	$ 1,194	$ 9,817	$ 9,477	$ 5,270	$ 1,493	$ 20,226