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Overview - Additional Information (Detail) $ in Thousands |  | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jul. 01, 2021 USD ($) | Sep. 30, 2021 USD ($) Segment | Jul. 22, 2021 USD ($) | Jun. 30, 2021 USD ($) | Dec. 31, 2020 USD ($)
Basis Of Presentation And Accounting Policies [Line Items] |  |  |  |  |
Investment amount |  |  |  | $ 5,200 |
Expected period of costs to be realized to recognize assets |  | 1 year |  |  |
Capitalized costs to obtain contract |  | $ 1,996 |  |  | $ 1,805
Number of reportable segments | Segment |  | 2 |  |  |
Beckmann & Egle Industrieelektronik GmbH |  |  |  |  |
Basis Of Presentation And Accounting Policies [Line Items] |  |  |  |  |
Medical business segment unit amount acquired | $ 2,827 |  |  |  |
Forciot Oy | Gentherm Automotive Segment |  |  |  |  |
Basis Of Presentation And Accounting Policies [Line Items] |  |  |  |  |
Investment amount |  |  | $ 2,357 |  |

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