Accumulated Other Comprehensive Income - Changes in AOCI (Details) $ in Thousands	6 Months Ended
	Jun. 27, 2015 USD ($)
Changes in Accumulated Other Comprehensive Income, by Component
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	$ (4,085)
Other comprehensive income (loss) before reclassifications	(2,581)
Amounts reclassified from accumulated other comprehensive income	74
Net current period other comprehensive income (loss)	(2,507)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(6,592)
Unrealized Gains and Losses on Available-for- Sale Securities [Member]
Changes in Accumulated Other Comprehensive Income, by Component
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(859)
Other comprehensive income (loss) before reclassifications	(222)
Amounts reclassified from accumulated other comprehensive income	74
Net current period other comprehensive income (loss)	(148)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(1,007)
Foreign Currency Items [Member]
Changes in Accumulated Other Comprehensive Income, by Component
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(3,226)
Other comprehensive income (loss) before reclassifications	(2,359)
Amounts reclassified from accumulated other comprehensive income	0
Net current period other comprehensive income (loss)	(2,359)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (5,585)