Reclassification Out of Accumulated Other Comprehensive Income to Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2016	Jul. 05, 2015	Jul. 03, 2016	Jul. 05, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	$ 1,666	$ 1,674	$ 3,308	$ 3,490
Reclassifications, net of tax	75	305	238	708
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			(134)	(561)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	83	74	163	147
Accumulated Defined Benefit Plans Adjustment, Net Prior Services Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	(59)		(59)
Defined Benefit Pension and Postretirement Plans, Net Gain (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	24	74	104	147
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	$ 51	$ 231	$ 134	$ 561