Note 3 - Revenue Recognition - Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
Jun. 30, 2018	Jun. 24, 2017
Performance obligations satisfied	$ 559
Changes in estimates	(29)
Performance obligations satisfied	2,313
Revenue	2,843	$ 1,991
Service [Member]
Revenue	$ 2,843	$ 1,675

Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in estimate of transaction price which increases (decreases) the asset and liability balance.

No definition available.

+ Details

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Namespace Prefix:	giga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized from performance obligation satisfied or partially satisfied in the current reporting period.

+ References

No definition available.

+ Details

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Namespace Prefix:	giga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of revenue recognized from performance obligation satisfied or partially satisfied in previous reporting periods. Includes, but is not limited to, change in transaction price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12A
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL108322424-203045

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- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

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Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: