Financial Instruments - Cash, Cash Equivalents and Short-Term Investments and Long-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 28, 2019	Dec. 29, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 41,981	$ 39,190
Unrealized Holding Gains	43	5
Unrealized Holding Losses	0	32
Fair Value	42,024	39,163
Cash and Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	19,767	18,715
Fair Value	19,767	18,715
Cash and Cash Equivalents \| U.S. treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		2,046
Fair Value		2,046
Cash and Cash Equivalents \| Cash
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,512	13,334
Fair Value	16,512	13,334
Cash and Cash Equivalents \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,255	3,335
Fair Value	3,255	3,335
Cash and Cash Equivalents \| Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,000
Fair Value	3,001
Cash and Cash Equivalents \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,891
Fair Value	1,893
Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,691	16,097
Unrealized Holding Gains	29	1
Unrealized Holding Losses		22
Fair Value	16,720	16,076
Short-term Investments \| Corporate bonds and medium-term notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,383	4,759
Unrealized Holding Gains	25
Unrealized Holding Losses		13
Fair Value	6,408	4,746
Short-term Investments \| Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		500
Unrealized Holding Losses		2
Fair Value		498
Short-term Investments \| U.S. treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,417	3,297
Unrealized Holding Gains	1
Unrealized Holding Losses		5
Fair Value	5,418	3,292
Short-term Investments \| Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		5,299
Unrealized Holding Gains	1	1
Unrealized Holding Losses		1
Fair Value		5,299
Short-term Investments \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		2,242
Unrealized Holding Gains	2
Unrealized Holding Losses		1
Fair Value		2,241
Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,523	4,378
Unrealized Holding Gains	14	4
Unrealized Holding Losses	0	10
Fair Value	5,537	4,372
Long-term Investments \| Corporate bonds and medium-term notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,530	2,879
Unrealized Holding Gains	12	4
Unrealized Holding Losses		4
Fair Value	2,542	2,879
Long-term Investments \| U.S. treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,494	999
Unrealized Holding Gains	1
Unrealized Holding Losses		6
Fair Value	2,495	993
Long-term Investments \| Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	499	500
Unrealized Holding Gains	1
Fair Value	$ 500	$ 500

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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-Publisher FASB
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-Topic 320
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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