Cash, Cash Equivalents, and Investments (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Apr. 01, 2018
Cash and Cash Equivalents [Abstract]
Gross realized gains on sale of investments	$ 64	$ 55
Gross realized losses on sale of investments	$ 24	$ 33

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

No definition available.

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