Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and interest expense	$ (5,427)	$ (3,292)	$ (11,407)	$ (6,812)
Reclassifications, net of tax			(1,346)	313
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			(1,469)	177
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	61	68	123	136
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	260	151	(1,346)	313
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 and interest expense	$ 199	$ 83	$ (1,469)	$ 177