Changes in Accumulated Other Comprehensive Income Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ 4,000
Other comprehensive income before reclassifications, net of tax			2,304
Amounts reclassified from accumulated other comprehensive income, net of tax	(346)	(137)	(595)	(350)
Other comprehensive income (loss)	819	(1,600)	1,709	(1,613)
Ending balance	5,709		5,709
Unrealized Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			1,381
Other comprehensive income before reclassifications, net of tax			2,304
Amounts reclassified from accumulated other comprehensive income, net of tax			(448)
Other comprehensive income (loss)			1,856
Ending balance	3,237		3,237
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			(147)
Other comprehensive income (loss)			(147)
Ending balance	$ 2,472		$ 2,472