Supplemental Quarterly Financial Data (Unaudited) - Prior Period Cash Flow Statement Adjustments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Jun. 28, 2014	Jun. 29, 2013	Sep. 27, 2014	Sep. 28, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows from Operating Activities
Net Income	$ 2,933	$ 6,619	$ 5,159	$ 6,985	$ 5,666	$ 3,971	$ 11,778	$ 9,637	$ 14,711	$ 16,622	$ 19,867	$ 11,378	$ 17,623
Deferred income taxes			(604)			(1,883)	998	1,868	2,073	833	345	(1,551)	1,098
Inventories			(8,388)			(993)	(1,694)	(357)	(4,961)	(1,055)	(2,335)	6,962	5,870
Accrued and other liabilities			(6,067)			(12,386)	835	(3,775)	(5,400)	(12,819)	6,103	(9,153)	(4,892)
As Reported
Cash Flows from Operating Activities
Net Income	2,622	6,472	4,629	4,636	5,504	3,707	11,101	9,211	13,723	13,847		9,343	16,437
Deferred income taxes			(919)			(2,040)	595	1,615	1,775	45		(2,242)	(142)
Inventories			(8,388)			(1,084)	(1,694)	(588)	(4,961)	(206)		7,811	6,185
Accrued and other liabilities			$ (6,067)			$ (12,386)	$ 835	$ (3,775)	$ (5,400)	$ (12,819)		$ (9,143)	$ (5,008)