Quarterly Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 28, 2012	Jun. 29, 2012	Mar. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jul. 01, 2011	Apr. 01, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of selected quarterly financial data
Net sales	$ 303,759	$ 290,601	$ 325,088	$ 353,630	$ 334,421	$ 392,794	$ 424,710	$ 374,805	$ 1,273,078	$ 1,526,730	$ 1,302,314
Gross margin	43,972	52,369	53,024	49,418	39,500	57,350	62,671	55,800	198,783	215,321	222,648
Percent of sales	14.50%	18.00%	16.30%	14.00%	11.80%	14.60%	14.80%	14.90%	15.60%	14.10%
Net income	$ 2,503	$ 8,114	$ 7,929	$ 6,118	$ 762	$ 13,527	$ 13,872	$ 11,818	$ 24,664	$ 39,979	$ 46,427
Net income per share of common stock:
Basic	$ 0.12	$ 0.40	$ 0.39	$ 0.30	$ 0.04	$ 0.66	$ 0.68	$ 0.58	$ 1.21	$ 1.96	$ 2.29
Diluted	$ 0.12	$ 0.39	$ 0.38	$ 0.30	$ 0.04	$ 0.65	$ 0.67	$ 0.57	$ 1.19	$ 1.93	$ 2.25
Dividends per share of common stock	$ 0.075	$ 0.075	$ 0.075	$ 0					$ 0.225	$ 0	$ 0
Stock price range:
High	$ 25.93	$ 25.57	$ 29.37	$ 32.91	$ 30.15	$ 42.05	$ 44.00	$ 44.94
Low	$ 18.84	$ 17.59	$ 20.37	$ 24.77	$ 19.53	$ 21.11	$ 33.02	$ 33.99