Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2014	Mar. 31, 2013
Net unrealized gains on marketable securities arising during period, tax	$ 654	$ 115
Reclassification adjustment for net gains included in net income, tax	(102)	(83)
Amortization of prior service benefit, tax	$ (42)	$ (40)