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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

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- Definition

Impairment loss on prepaid licensing and royalty fees.

+ References

No definition available.

+ Details

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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