Income Taxes - Provision for Income Taxes (Details) (USD $) In Thousands, 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
Domestic and foreign components of income before income taxes are as follows:
Domestic									$ 14,885	$ 22,313	$ 23,028
Foreign									2,053	2,026	2,417
Income before income taxes	1,607	4,538	5,415	5,378	6,010	5,963	6,293	6,073	16,938	24,339	25,445
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current U.S. federal									4,023	6,133	6,778
Current Foreign									1,505	1,469	1,393
Current U.S. state and local									831	1,409	993
Current Total current tax									6,359	9,011	9,164
Deferred tax:
Deferred U.S. federal									273	(245)	55
Deferred Foreign									(97)	(34)	0
Deferred U.S. state and local									53	(72)	61
Deferred income taxes									229	(351)	116
Total tax	382	1,812	2,182	2,212	2,306	2,100	2,238	2,016	6,588	8,660	9,280
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at statutory rate of 35% / 34%									5,928	8,519	8,906
State tax, net of federal benefit									578	877	685
Non-taxable income									(520)	(563)	(993)
Non-deductible expenses									803	963	796
Change in estimate primarily related to foreign taxes									134	128	41
Change in estimate primarily related to state taxes and tax reserves									0	(172)	50
Change in estimate primarily related to U.S. federal taxes									0	0	(157)
Tax credits									(421)	(1,117)	0
Other, net									$ 86	$ 25	$ (48)
Effective income tax rate									38.90%	35.60%	36.50%