| Cover Page - USD ($) $ in Billions | 12 Months Ended | ||
| Dec. 31, 2021 | Mar. 01, 2022 | Jun. 30, 2021 | |
| Document And Entity Information [Line Items] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | true | ||
| Document Period End Date | Dec. 31, 2021 | ||
| Document Fiscal Year Focus | 2021 | ||
| Document Fiscal Period Focus | FY | ||
| Document Annual Report | true | ||
| Document Transition Report | false | ||
| Entity Registrant Name | QUANTUMSCAPE CORPORATION | ||
| Entity Central Index Key | 0001811414 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity Well-known Seasoned Issuer | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Emerging Growth Company | false | ||
| Entity Small Business | false | ||
| ICFR Auditor Attestation Flag | true | ||
| Entity Shell Company | false | ||
| Entity Incorporation, State or Country Code | DE | ||
| Entity File Number | 001-39345 | ||
| Entity Tax Identification Number | 85-0796578 | ||
| Entity Address, Address Line One | 1730 Technology Drive | ||
| Entity Address, City or Town | San Jose | ||
| Entity Address, State or Province | CA | ||
| Entity Address Postal Zip Code | 95110 | ||
| City Area Code | 408 | ||
| Local Phone Number | 452-2000 | ||
| Entity Public Float | $ 7.2 | ||
| Title of 12(b) Security | Class A Common Stock, par value $0.0001 per share | ||
| Trading Symbol | QS | ||
| Security Exchange Name | NYSE | ||
| Documents Incorporated by Reference | DOCUMENTS INCORPORATED BY REFERENCE None. | ||
| Auditor Name | Ernst & Young LLP | ||
| Auditor Firm ID | 42 | ||
| Auditor Location | Redwood City, California | ||
| Amendment Description | On February 28, 2022, QuantumScape Corporation (“QuantumScape,” the “Company,” “we,” “us,” or “our”) filed its Annual Report on Form 10-K for the fiscal year ended December 31, 2021 (the “Original Filing”). As disclosed in the Original Filing, we are filing this Annual Report on Form 10-K/A (the “Amendment”) as Amendment No. 1 to the Original Filing for the purposes of amending Part III, Items 10, 11, 12, 13 and 14 of the Original Filing to include the information required by such Items. In addition, pursuant to the rules of the Securities and Exchange Commission (the “SEC”), we have also included as exhibits currently dated certifications required under Section 302 of The Sarbanes-Oxley Act of 2002. We are amending and refiling Part IV to reflect the inclusion of those certifications. Because no financial statements are contained within this Amendment, we are not including certifications pursuant to Section 906 of The Sarbanes-Oxley Act of 2002. Except as described above, no other changes have been made to the Original Filing. Except as otherwise indicated herein, we have not updated the disclosures contained in the Original Filing to reflect any events that occurred subsequent to the date of the Original Filing. Accordingly, this Amendment should be read in conjunction with the Original Filing and the Company’s other and subsequent filings with the SEC. | ||
| Common Class A [Member] | |||
| Document And Entity Information [Line Items] | |||
| Entity Common Stock, Shares Outstanding | 334,793,716 | ||
| Common Class B [Member] | |||
| Document And Entity Information [Line Items] | |||
| Entity Common Stock, Shares Outstanding | 95,267,246 |
