Earnings Per Share (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
Numerator for basic and diluted EPS
Net income	$ 2,503	$ 8,114	$ 7,929	$ 6,118	$ 762	$ 13,527	$ 13,872	$ 11,818	$ 24,664	$ 39,979	$ 46,427
Denominator for basic EPS:
Weighted-average shares outstanding									20,418	20,365	20,282
Effective of dilutive securities:
Stock options and stock appreciation rights									163	237	156
Restricted stock									94	152	151
Performance restricted shares									4	0	1
Diluted potential common shares									261	389	308
Denominator for diluted EPS:
Weighted-average shares outstanding									20,679	20,754	20,590
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