Reclassification Out of Accumulated Other Comprehensive Income to Statement of Operations (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]
Interest income	$ (2,892)	$ (1,708)	$ (6,201)	$ (5,198)
Reclassifications, net of tax			(653)	(1,029)
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			468	808
Amortization of prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	81	74	244	221
Prior service cost arising during period
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			(59)
Retirement Plans Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	81	74	185	221
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	415	321	653	1,029
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	$ 334	$ 247	$ 468	$ 808