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v3.20.4

Overview - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2020
Europe |
Basis Of Presentation And Accounting Policies [Line Items] |
Production capacity percentage (impact of COVID-19) | 70.00%

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- Definition Basis of presentation and accounting policies. + References No definition available. + Details
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Namespace Prefix: | thrm_
Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition Production capacity percentage. + References No definition available. + Details
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Namespace Prefix: | thrm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_StatementGeographicalAxis=srt_EuropeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |