Changes in Accumulated Other Comprehensive Income Balances (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2014	Mar. 31, 2013	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income before reclassifications, tax	$ 654	$ 115
Amounts reclassified from accumulated other comprehensive income, tax	(102)	(83)
Amounts reclassified from accumulated other comprehensive income, tax	(42)	(40)
Unrealized gains on marketable securities, tax	1,346		794
Retirement plans prior service benefit, tax	(326)		(284)
Unrealized Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income before reclassifications, tax	654
Amounts reclassified from accumulated other comprehensive income, tax	(102)
Retirement Plans Prior Service Benefit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income, tax	$ (42)