Cash, Cash Equivalents, and Investments (Detail) - USD ($)	3 Months Ended	6 Months Ended
Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016
Cash and Cash Equivalents [Abstract]
Gross realized gains on sale of investments	$ 55,000	$ 141,000	$ 143,000	$ 225,000
Gross realized losses on sale of investments	$ 13,000	$ 0	$ 36,000	$ 97,000

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=73527792&loc=d3e27357-111563

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