Reclassifications Out of Accumulated Other Comprehensive (Loss) Income to Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 80	$ 60	$ 183	$ 95
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	42	13	106	2
Amortization of prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 38	$ 47	$ 77	$ 93