Debt issuance cost.

No definition available.

Name:	thrm_DebtIssuanceCost
Namespace Prefix:	thrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line of credit facility increase in maximum borrowing capacity.

+ References

No definition available.

+ Details

Name:	thrm_LineOfCreditFacilityIncreaseInMaximumBorrowingCapacity
Namespace Prefix:	thrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of credit facility increase maximum borrowings subject to specific conditions.

+ References

No definition available.

+ Details

Name:	thrm_LineOfCreditFacilityIncreaseMaximumBorrowingsSubjectToSpecificConditions
Namespace Prefix:	thrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of stock interest on subsidiaries pledge to secure obligation.

+ References

No definition available.

+ Details

Name:	thrm_PercentageOfStockInterestOnSubsidiariesPledgeToSecureObligation
Namespace Prefix:	thrm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
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-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
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-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

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+ Details

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

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

+ Details

Name:	us-gaap_WriteOffOfDeferredDebtIssuanceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=thrm_SecondAmendedAndRestatedCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=thrm_BaseRateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=thrm_TermSofrRateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=thrm_LettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=thrm_SwingLineLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=thrm_UnitedStateRevolvingNoteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Additional Information (Detail) - USD ($)			9 Months Ended
Debt - Additional Information (Detail) - USD ($)	Jun. 10, 2022	Jun. 27, 2019	Sep. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Maximum percentage of stock of non US subsidiaries pledge to secure obligation			66.00%
Unamortized deferred debt issuance costs written off			$ 144,000
Second Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Debt issuance cost	$ 1,417,000
Remaining borrowing capacity			$ 264,460,000
Second Amended and Restated Credit Agreement \| Federal Funds Rate
Debt Instrument [Line Items]
Interest rate			0.50%
Second Amended and Restated Credit Agreement \| SOFR Rate
Debt Instrument [Line Items]
Interest rate			1.00%
Base Rate Loans \| Second Amended and Restated Credit Agreement \| Minimum
Debt Instrument [Line Items]
Interest rate			0.125%
Base Rate Loans \| Second Amended and Restated Credit Agreement \| Maximum
Debt Instrument [Line Items]
Interest rate			1.125%
Term SOFR Rate Loans \| Second Amended and Restated Credit Agreement \| Minimum
Debt Instrument [Line Items]
Interest rate			1.125%
Term SOFR Rate Loans \| Second Amended and Restated Credit Agreement \| Maximum
Debt Instrument [Line Items]
Interest rate			2.125%
Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity increase subject to specified conditions	200,000,000
Revolving Credit Facility \| Letters of Credit
Debt Instrument [Line Items]
Line of credit, outstanding amount			$ 0	$ 0
Revolving Credit Facility \| Swing Line Loans
Debt Instrument [Line Items]
Maximum borrowing capacity	50,000,000
Revolving Credit Facility \| Second Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	500,000,000
Line of credit, outstanding amount	$ 35,000,000
Debt maturity date	Jun. 10, 2027
Increase in maximum borrowing capacity	$ 25,000,000
Revolving Credit Facility \| Second Amended and Restated Credit Agreement \| Minimum
Debt Instrument [Line Items]
Commitment fee percentage payable on average daily unused amounts			0.175%
Revolving Credit Facility \| Second Amended and Restated Credit Agreement \| Maximum
Debt Instrument [Line Items]
Commitment fee percentage payable on average daily unused amounts			0.30%
Revolving Credit Facility \| Revolving Note (U.S. Dollar)
Debt Instrument [Line Items]
Debt maturity date		Jun. 27, 2024
Standby Letters of Credit \| Second Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000,000