Changes in Accumulated Other Comprehensive Income Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 4,000
Other comprehensive income before reclassifications, net of tax	1,139
Amounts reclassified from accumulated other comprehensive income, net of tax	(249)	(213)
Other comprehensive income (loss)	890	(13)
Ending balance	4,890
Unrealized Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,381
Other comprehensive income before reclassifications, net of tax	1,139
Amounts reclassified from accumulated other comprehensive income, net of tax	(176)
Other comprehensive income (loss)	963
Ending balance	2,344
Retirement Plans Prior Service Benefit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	2,619
Amounts reclassified from accumulated other comprehensive income, net of tax	(73)
Other comprehensive income (loss)	(73)
Ending balance	$ 2,546