Selected Quarterly Financial Data (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 Financial Information Disclosure [Abstract]
Net sales	$ 201,244	$ 181,885	$ 189,695	$ 194,316	$ 185,577	$ 172,814	$ 183,236	$ 183,450	$ 767,140	$ 725,077	$ 713,723
Gross profit	107,287	97,913	99,732	100,911	96,452	91,311	91,455	95,716	405,843	374,934	365,384
Net income (loss)	$ 10,897	$ 9,320	$ 10,296	$ 9,968	$ (25,134)	$ 8,211	$ 8,680	$ 8,995	$ 40,481	$ 752	$ 30,346
EPS:
Basic (per share)	$ 0.38	$ 0.33	$ 0.36	$ 0.36	$ (0.90)	$ 0.29	$ 0.31	$ 0.32	$ 1.43	$ 0.03	$ 1.06
Diluted (per share)	$ 0.38	$ 0.32	$ 0.36	$ 0.35	$ (0.90)	$ 0.29	$ 0.30	$ 0.31	$ 1.41	$ 0.03	$ 1.05