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Reconciliation of Beginning and Ending Amounts of Valuation Allowance on Deferred Tax Assets (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Valuation Allowance [Abstract] |  |  |
Balance at beginning of year | $ 13,046 | $ 12,732 | $ 11,765
Subsequent reversal and utilization of valuation allowance | (81) | (87) | (17)
Changes to valuation allowance | 575 | 1,585 | 723
Expirations | (221) | (1,720) |
Exchange differences | 288 | 536 | 261
Balance at end of year | $ 13,607 | $ 13,046 | $ 12,732

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- Definition Deferred tax assets expirations. + References No definition available. + Details
Name: | gigm_DeferredTaxAssetsExpirations
Namespace Prefix: | gigm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Deferred Tax Assets Valuation Allowances Currency Translation Increase Decrease + References No definition available. + Details
Name: | gigm_DeferredTaxAssetsValuationAllowancesCurrencyTranslationIncreaseDecrease
Namespace Prefix: | gigm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Reversal of deferred tax asset valuation allowance. + References No definition available. + Details
Name: | gigm_ReversalOfDeferredTaxAssetValuationAllowance
Namespace Prefix: | gigm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319 + Details
Name: | us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

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- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319 + Details
Name: | us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration