Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 26, 2014	Jun. 27, 2014	Mar. 28, 2014	Dec. 31, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator for basic and diluted EPS:
Net income	$ 11,976	$ 12,440	$ 9,974	$ 7,331	$ 3,775	$ 4,992	$ 4,155	$ 6,785	$ 41,721	$ 19,707	$ 24,664
Denominator for basic EPS:
Weighted-average shares outstanding (in shares)									20,461	20,571	20,418
Effect of dilutive securities:
Stock options and stock appreciation rights (in shares)									185	188	163
Restricted stock (in shares)									95	101	94
Performance-based restricted shares (in shares)									69	35	4
Diluted potential common shares (in shares)									349	324	261
Denominator for diluted EPS:
Adjusted weighted-average shares outstanding (in shares)									20,810	20,895	20,679
Basic EPS (in dollars per share)	$ 0.59	$ 0.61	$ 0.48	$ 0.36	$ 0.18	$ 0.24	$ 0.20	$ 0.33	$ 2.04	$ 0.96	$ 1.21
Diluted EPS (in dollars per share)	$ 0.58	$ 0.60	$ 0.47	$ 0.35	$ 0.18	$ 0.24	$ 0.20	$ 0.33	$ 2.00	$ 0.94	$ 1.19