Selected Quarterly Financial Data (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
Selected Quarterly Financial Information [Abstract]
Net sales	$ 163,287	$ 166,617	$ 159,239	$ 144,663	$ 143,313	$ 160,577	$ 169,806	$ 161,555	$ 633,806	$ 635,251	$ 612,886
Gross profit	43,247	43,605	41,028	33,706	35,495	45,194	55,615	57,393	161,586	193,697	224,869
Net income attributable to common stockholders	$ 4,075	$ 8,553	$ 6,653	$ 4,871	$ 3,115	$ 9,957	$ 17,981	$ 19,684	$ 24,152	$ 50,737	$ 76,733
Earnings per share attributable to common shareholders
Basic	$ 0.09	$ 0.19	$ 0.15	$ 0.11	$ 0.07	$ 0.22	$ 0.38	$ 0.44	$ 0.53	$ 1.12	$ 1.74
Diluted	$ 0.09	$ 0.18	$ 0.14	$ 0.10	$ 0.07	$ 0.21	$ 0.37	$ 0.42	$ 0.51	$ 1.09	$ 1.68