Overview - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2022	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Investment amount	$ 5,200	$ 5,200
Capitalized costs to obtain contract	$ 2,085	$ 1,946
Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ownership interest	20.00%
Minimum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Expected period of costs to be realized to recognize assets	1 year

Expected period of costs to be realized to recognize assets.

No definition available.

Name:	thrm_ExpectedPeriodOfCostsToBeRealizedToRecognizeAssets
Namespace Prefix:	thrm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Organization, consolidation and presentation of financial statements.

+ References

No definition available.

+ Details

Name:	thrm_OrganizationConsolidationAndPresentationOfFinancialStatementsLineItems
Namespace Prefix:	thrm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126905575&loc=SL49131252-203054

+ Details

Name:	us-gaap_CapitalizedContractCostNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Portion of equity (net assets) in a variable interest entity (VIE) not attributable, directly or indirectly, to the parent entity. That is, this is the portion of equity in a VIE that is attributable to the noncontrolling interest (previously referred to as minority interest).

+ References

No definition available.

+ Details

Name:	us-gaap_NoncontrollingInterestInVariableInterestEntity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: