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v3.21.1

Deferred Revenue - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2017
Deferred Revenue [Abstract] |  |  |
Breakage amount recognized as revenue | $ 51 | $ 63 |
Cumulative breakage amount recognized as revenue |  |  | $ 346

X
- Definition Breakage amount recognized as revenue. + References No definition available. + Details
Name: | gigm_BreakageAmountRecognizedAsRevenue
Namespace Prefix: | gigm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Cumulative breakage amount recognized as revenue. + References No definition available. + Details
Name: | gigm_CumulativeBreakageAmountRecognizedAsRevenue
Namespace Prefix: | gigm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_DeferredRevenueAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration