Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
Net unrealized gains on marketable securities arising during period, tax (benefit) expense	$ (139)	$ 358	$ 1,103	$ (367)
Reclassification adjustment for net gains included in net income, tax (benefit)	(348)	(109)	(591)	(231)
Amortization of prior service benefit, tax (benefit)	$ (42)	$ (40)	$ (127)	$ (119)