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Prepaid Licensing and Royalty Fees - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract] |  |  |
Impairment losses on prepaid licensing and royalty fees | $ 0 | $ 85 | $ 244

X
- Definition Impairment loss on prepaid licensing and royalty fees. + References No definition available. + Details
Name: | gigm_ImpairmentLossOnPrepaidLicensingAndRoyaltyFees
Namespace Prefix: | gigm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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