Marketable Securities - Schedule of Market Value, Cost and Unrealized Gains on Equity Securities (Detail) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Marketable securities	$ 9,139	$ 9,333
Cost	8,404	11,143
Unrealized gain (loss)	$ 735	$ (1,810)

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

Name:	us-gaap_EquitySecuritiesFvNi
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant