Cash, Cash Equivalents, and Investments (Detail) - USD ($) $ in Thousands	3 Months Ended
Apr. 01, 2018	Apr. 02, 2017
Cash and Cash Equivalents [Abstract]
Gross realized gains on sale of investments	$ 55	$ 88
Gross realized losses on sale of investments	$ 33	$ 23

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

Name:	us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration