Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 04, 2015	Jun. 28, 2014	Jul. 04, 2015	Jun. 28, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2014			$ (1,259)
Other comprehensive income before reclassifications			42
Amounts reclassified from accumulated OCI			104
Net other comprehensive income	$ 2	$ (7)	146	$ (78)
Balance as of July 4, 2015	(1,113)		(1,113)
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2014			(121)
Other comprehensive income before reclassifications			42
Amounts reclassified from accumulated OCI			0
Net other comprehensive income			42
Balance as of July 4, 2015	(79)		(79)
Post Retirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2014			(1,138)
Other comprehensive income before reclassifications			0
Amounts reclassified from accumulated OCI			104
Net other comprehensive income			104
Balance as of July 4, 2015	$ (1,034)		$ (1,034)