Reclassification Out of Accumulated Other Comprehensive Income to Statement of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2016	Oct. 04, 2015	Oct. 02, 2016	Oct. 04, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 196	$ 168	$ 257	$ 462
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	150	126	152	335
Amortization of prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	(46)	(42)	(139)	(127)
Prior service cost arising during period
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 0	$ 0	$ (34)	$ 0