New Accounting Pronouncements (Policies)	3 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited consolidated condensed financial statements included herein have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to those rules and regulations. The information furnished in the consolidated condensed financial statements include all adjustments (consisting of only normal, recurring adjustments), considered necessary to present fairly the results of operations, financial position and cash flows of the Company. These financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The operating results for interim periods are not necessarily indicative of results that may be expected for any other interim period or for the full year. In preparing these financial statements, management was required to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. These estimates and assumptions are based on our historical experience, the terms of existing contracts, our evaluation of trends in the industry, information provided by our customers and suppliers and information available from other outside sources, as appropriate. These estimates and assumptions are subject to an inherent degree of uncertainty. We are not presently aware of any events or circumstances that would require us to update such estimates and assumptions or revise the carrying value of our assets or liabilities. Our estimates may change, however, as new events occur and additional information is obtained. As a result, actual results may differ significantly from our estimates, and any such differences may be material to our financial statements.
Impact of COVID-19	Impact of COVID-19 The COVID-19 pandemic began in China around December 2019. The impact of the outbreak quickly expanded beyond China and its surrounding region. The COVID-19 pandemic significantly disrupted and adversely impacted global economic activity and the global automotive markets in the first half of 2020, which had significant negative impacts on Gentherm’s financial performance in the first half of 2020. During the first quarter of 2020, customer plants in North America and Europe were closed beginning in the second half of March due to the pandemic. This resulted in temporary, partial closures of several of our manufacturing facilities in North America and Europe by the end of March 2020. Customer plants and our manufacturing facilities in Asia were closed for several weeks in February and operated at reduced volumes in March 2020, resuming production to near full capacity by the end of the first quarter, which continued throughout the second quarter of 2020. Other adverse impacts of the pandemic include supply chain and production disruptions, workforce restrictions, travel restrictions and reduced consumer spending. We significantly recovered in the second half of 2020, with increased strong production volumes versus the first half of that year and stronger than pre-COVID levels. This recovery continued in the first quarter of 2021. However, the COVID-19 pandemic is ongoing globally and continues to have a significant impact on global automotive markets in 2021, in the form of supply chain and production disruptions, workforce restrictions and travel restrictions, among other factors, and we remain subject to related risks. The increased consumer demand and vehicle production schedules in the second half of 2020, particularly in the fourth quarter, was unexpected in certain areas of our supply chain. This surge in demand, as well as a significant increased consumer demand for personal electronics, during the latter half of 2020 led to a worldwide semiconductor supply shortage in early 2021. Semiconductor suppliers have not been able to quickly reallocate production lines to serve the full capacity needs of the automotive industry. Other recent pandemic-related issues have exacerbated port congestion and intermittent supplier shutdowns and delays, resulting in additional expenses to expedite delivery of critical parts and manufacturing delays. Our suppliers also have experienced plant closures and production delays, and may continue to experience delays in manufacturing the materials and products we require according to our schedule and specifications. We are working closely with our suppliers and customers to minimize any potential adverse impacts, and we continue to closely monitor the availability of semiconductor microchips and other component parts and raw materials, customer vehicle production schedules and any other supply chain inefficiencies that may arise. The consequences of the pandemic and adverse impact to the economy continue to evolve and the future adverse impact on our business and financial statements remains subject to significant uncertainty as of the date of this filing.
Segment Reporting	Segment Reporting The Company has two reportable segments: Automotive, which includes automotive climate comfort systems, automotive cable systems, battery performance solutions and automotive electronic and software systems; and Medical. In 2020, the previously-named Industrial reporting segment was renamed the Medical reporting segment to reflect the patient temperature management business as the focus and strategic direction of this segment. Also, during 2020, the advanced research and development costs not associated with the Medical segment were presented within the Automotive segment, as this organization primarily supports the Automotive related research and development activities following the divestitures of our former remote power generation systems business, Gentherm Global Power Technologies (“GPT”) and our former environmental test equipment business, Cincinnati Sub Zero industrial chamber business (“CSZ-IC”).
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Income Taxes In December 2019, the FASB issued ASU No. 2019-12, "Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes". This ASU simplifies the accounting for income taxes by removing certain exceptions previously included in the guidance. In addition, the ASU amends existing guidance to improve consistent application. ASU 2019-12 is effective for annual reporting periods beginning after December 15, 2020, and interim periods within those reporting periods. The Company adopted ASU 2019-12 as of January 1, 2021 and there was no significant impact on its consolidated condensed financial statements and related disclosures as a result.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted Reference Rate Reform In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of Effects of Reference Rate Reform on Financial Reporting”. ASU 2020-04 provides practical expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The expedients and exceptions provided by the amendments in this update apply only to contracts, hedging relationships, and other transactions that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued as a result of reference rate reform. These amendments are not applicable to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. In January 2021, the FASB subsequently issued ASU 2021-01, “Reference Rate Reform (Topic 848): Scope” to clarify that certain optional expedients and exceptions in Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. ASU 2020-04 and ASU 2021-01 is effective as of March 12, 2020 through December 31, 2022 and may be applied retrospectively to contract modifications and hedging relationships from the beginning of an interim period that includes or is subsequent to March 12, 2020, or on a prospective basis to new modifications from any date within an interim period that includes or is subsequent to the date of the issuance of a final Update, up to the date that financial statements are available to be issued. The Company will adopt this standard when LIBOR is discontinued and does not expect a material impact to its consolidated financial statements.

New Accounting Pronouncements (Policies)

3 Months Ended

Mar. 31, 2021

The unaudited consolidated condensed financial statements included herein have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to those rules and regulations. The information furnished in the consolidated condensed financial statements include all adjustments (consisting of only normal, recurring adjustments), considered necessary to present fairly the results of operations, financial position and cash flows of the Company. These financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The operating results for interim periods are not necessarily indicative of results that may be expected for any other interim period or for the full year.

In preparing these financial statements, management was required to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. These estimates and assumptions are based on our historical experience, the terms of existing contracts, our evaluation of trends in the industry, information provided by our customers and suppliers and information available from other outside sources, as appropriate. These estimates and assumptions are subject to an inherent degree of uncertainty. We are not presently aware of any events or circumstances that would require us to update such estimates and assumptions or revise the carrying value of our assets or liabilities. Our estimates may change, however, as new events occur and additional information is obtained. As a result, actual results may differ significantly from our estimates, and any such differences may be material to our financial statements.

Impact of COVID-19

The COVID-19 pandemic began in China around December 2019. The impact of the outbreak quickly expanded beyond China and its surrounding region. The COVID-19 pandemic significantly disrupted and adversely impacted global economic activity and the global automotive markets in the first half of 2020, which had significant negative impacts on Gentherm’s financial performance in the first half of 2020. During the first quarter of 2020, customer plants in North America and Europe were closed beginning in the second half of March due to the pandemic. This resulted in temporary, partial closures of several of our manufacturing facilities in North America and Europe by the end of March 2020. Customer plants and our manufacturing facilities in Asia were closed for several weeks in February and operated at reduced volumes in March 2020, resuming production to near full capacity by the end of the first quarter, which continued throughout the second quarter of 2020. Other adverse impacts of the pandemic include supply chain and production disruptions, workforce restrictions, travel restrictions and reduced consumer spending. We significantly recovered in the second half of 2020, with increased strong production volumes versus the first half of that year and stronger than pre-COVID levels. This recovery continued in the first quarter of 2021. However, the COVID-19 pandemic is ongoing globally and continues to have a significant impact on global automotive markets in 2021, in the form of supply chain and production disruptions, workforce restrictions and travel restrictions, among other factors, and we remain subject to related risks.

The increased consumer demand and vehicle production schedules in the second half of 2020, particularly in the fourth quarter, was unexpected in certain areas of our supply chain. This surge in demand, as well as a significant increased consumer demand for

personal electronics, during the latter half of 2020 led to a worldwide semiconductor supply shortage in early 2021. Semiconductor suppliers have not been able to quickly reallocate production lines to serve the full capacity needs of the automotive industry. Other recent pandemic-related issues have exacerbated port congestion and intermittent supplier shutdowns and delays, resulting in additional expenses to expedite delivery of critical parts and manufacturing delays. Our suppliers also have experienced plant closures and production delays, and may continue to experience delays in manufacturing the materials and products we require according to our schedule and specifications. We are working closely with our suppliers and customers to minimize any potential adverse impacts, and we continue to closely monitor the availability of semiconductor microchips and other component parts and raw materials, customer vehicle production schedules and any other supply chain inefficiencies that may arise. The consequences of the pandemic and adverse impact to the economy continue to evolve and the future adverse impact on our business and financial statements remains subject to significant uncertainty as of the date of this filing.

Segment Reporting

The Company has two reportable segments: Automotive, which includes automotive climate comfort systems, automotive cable systems, battery performance solutions and automotive electronic and software systems; and Medical.

In 2020, the previously-named Industrial reporting segment was renamed the Medical reporting segment to reflect the patient temperature management business as the focus and strategic direction of this segment. Also, during 2020, the advanced research and development costs not associated with the Medical segment were presented within the Automotive segment, as this organization primarily supports the Automotive related research and development activities following the divestitures of our former remote power generation systems business, Gentherm Global Power Technologies (“GPT”) and our former environmental test equipment business, Cincinnati Sub Zero industrial chamber business (“CSZ-IC”).

Recently Adopted Accounting Pronouncements

Income Taxes

In December 2019, the FASB issued ASU No. 2019-12, "Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes". This ASU simplifies the accounting for income taxes by removing certain exceptions previously included in the guidance. In addition, the ASU amends existing guidance to improve consistent application. ASU 2019-12 is effective for annual reporting periods beginning after December 15, 2020, and interim periods within those reporting periods. The Company adopted ASU 2019-12 as of January 1, 2021 and there was no significant impact on its consolidated condensed financial statements and related disclosures as a result.

Recently Issued Accounting Pronouncements Not Yet Adopted

Reference Rate Reform

In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of Effects of Reference Rate Reform on Financial Reporting”. ASU 2020-04 provides practical expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The expedients and exceptions provided by the amendments in this update apply only to contracts, hedging relationships, and other transactions that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued as a result of reference rate reform. These amendments are not applicable to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. In January 2021, the FASB subsequently issued ASU 2021-01, “Reference Rate Reform (Topic 848): Scope” to clarify that certain optional expedients and exceptions in Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. ASU 2020-04 and ASU 2021-01 is effective as of March 12, 2020 through December 31, 2022 and may be applied retrospectively to contract modifications and hedging relationships from the beginning of an interim period that includes or is subsequent to March 12, 2020, or on a prospective basis to new modifications from any date within an interim period that includes or is subsequent to the date of the issuance of a final Update, up to the date that financial statements are

available to be issued. The Company will adopt this standard when LIBOR is discontinued and does not expect a material impact to its consolidated financial statements.

- Definition

Disclosure of accounting policy for segment reporting.

+ References + Details