| Document and Entity Information - USD ($) $ in Millions | 12 Months Ended | | |
| Dec. 31, 2023 | Mar. 12, 2024 | Jun. 30, 2023 |
| Cover [Abstract] | | | |
| Document Type | 10-K/A | | |
| Amendment Flag | true | | |
| Document Period End Date | Dec. 31, 2023 | | |
| Document Fiscal Year Focus | 2023 | | |
| Document Fiscal Period Focus | FY | | |
| Trading Symbol | KRTX | | |
| Entity Registrant Name | Karuna Therapeutics, Inc. | | |
| Entity Central Index Key | 0001771917 | | |
| Current Fiscal Year End Date | --12-31 | | |
| Entity File Number | 001-38958 | | |
| Entity Tax Identification Number | 27-0605902 | | |
| Entity Address, Address Line One | 99 High Street | | |
| Entity Address, Address Line Two | 26th Floor | | |
| Entity Address, City or Town | Boston | | |
| Entity Address, State or Province | MA | | |
| Entity Address, Postal Zip Code | 02110 | | |
| City Area Code | 857 | | |
| Local Phone Number | 449-2244 | | |
| Entity Current Reporting Status | Yes | | |
| Entity Filer Category | Large Accelerated Filer | | |
| Entity Small Business | false | | |
| Entity Emerging Growth Company | false | | |
| Entity Common Stock, Shares Outstanding | | 38,199,272 | |
| Entity Shell Company | false | | |
| Document Annual Report | true | | |
| Document Transition Report | false | | |
| Entity Interactive Data Current | Yes | | |
| Title of 12(b) Security | Common Stock, $0.0001 Par Value | | |
| Security Exchange Name | NASDAQ | | |
| Entity Incorporation, State or Country Code | DE | | |
| Entity Well-known Seasoned Issuer | Yes | | |
| Entity Voluntary Filers | No | | |
| Document Financial Statement Error Correction [Flag] | false | | |
| Entity Public Float | | | $ 5,872.6 |
| ICFR Auditor Attestation Flag | true | | |
| Documents Incorporated by Reference | None. | | |
| Amendment Description | Karuna Therapeutics, Inc., is filing this Amendment No. 1 (this “Amendment No. 1”) to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023 (the “2023 Annual Report”), filed with the Securities and Exchange Commission (the “SEC”) on February 22, 2024, only for the purpose of including the Part III information required under the instructions to Form 10-K and the general rules and regulations under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), which information was previously omitted from our 2023 Annual Report in reliance on General Instruction G(3) to Form 10-K, which permits the omitted information to be incorporated by reference in the 2023 Annual Report from our definitive proxy statement so long as such proxy statement is filed no later than 120 days after the end of the Company’s fiscal year. Except where the context otherwise requires or where otherwise indicated, the terms “Karuna,” “we,” “us,” “our,” “our company,” “the Company,” and “our business” refer to Karuna Therapeutics, Inc., a Delaware corporation, and its consolidated subsidiary. This Amendment No. 1 amends and restates only Part III, Items 10 (Directors, Executive Officers and Corporate Governance), 11 (Executive Compensation), 12 (Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters), 13 (Certain Relationships and Related Transactions, and Director Independence) and 14 (Principal Accountant Fees and Services) of our 2023 Annual Report filed with the SEC on February 22, 2024, in their entirety as set forth herein. In addition, this Amendment No. 1 deletes the reference on the cover page of our 2023 Annual Report to the incorporation by reference of portions of our proxy statement into Part III of such 2023 Annual Report, as well as updates the outstanding share number referenced thereon. No other Items of our 2023 Annual Report filed with the SEC on February 22, 2024, have been amended or revised in this Amendment No. 1, and all such other Items shall be as set forth in such 2023 Annual Report. In addition, pursuant to SEC rules, Item 15 of Part IV of our 2023 Annual Report filed with the SEC on February 22, 2024, is hereby amended solely to include, as Exhibits 31.3 and 31.4, new certifications of our principal executive officer and principal financial officer pursuant to Rule 13a-14(a) under the Exchange Act. Because no financial statements have been included in this Amendment No. 1, and because this Amendment No. 1 does not contain or amend any disclosure with respect to paragraphs 3, 4 and 5 of Items 307 and 308 of Regulation S-K, the corresponding certifications have been omitted. We are not including the certifications under Section 906 of the Sarbanes-Oxley Act of 2002 as no financial statements are being filed with this Amendment No. 1. No other information has been updated for any subsequent events occurring after we filed our 2023 Annual Report with the SEC on February 22, 2024. Accordingly, this Amendment No. 1 should be read in conjunction with the 2023 Annual Report and our other filings made with the SEC subsequent to the filing of such 2023 Annual Report. | | |
| Auditor Firm ID | 185 | | |
| Auditor Name | KPMG LLP | | |
| Auditor Location | Boston, Massachusetts | | |
