| Document and Entity Information - USD ($) shares in Thousands | 12 Months Ended | | |
| Dec. 31, 2022 | Mar. 03, 2023 | Jun. 30, 2022 |
| Cover [Abstract] | | | |
| Entity Registrant Name | Oncternal Therapeutics, Inc. | | |
| Entity Central Index Key | 0001260990 | | |
| Document Type | 10-K/A | | |
| Document Period End Date | Dec. 31, 2022 | | |
| Amendment Flag | true | | |
| Amendment Description | This Amendment No. 1 on Form 10-K/A (this “Amendment”) amends the Annual Report on Form 10- for the fiscal year ended December 31, 2022 of Oncternal Therapeutics, Inc. (the “Original Filing”), as originally filed with the Securities and Exchange Commission (“SEC”) on March 9, 2022 (the “Original Filing Date”). This Amendment is being filed to amend: (i) Part III of the Original Filing to include the informatiKon required by Part III of Form 10-K that was previously omitted from the Original Filing in reliance on General Instruction G(3) to Form 10-K because a definitive proxy statement containing such information may not be filed within 120 days after the end of our fiscal year ended December 31, 2022; and (ii) Part IV of the Original Filing to add new certifications pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 as required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and in accordance with Rule 13a-14(a) under the Exchange Act.Because no financial statements of the registrant have been included in this Amendment and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4 and 5 of the new certifications pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 have been omitted. In addition, the reference on the cover of the Original Filing to the incorporation by reference to portions of our definitive proxy statement into Part III of the Original Filing is hereby deleted. This Amendment does not amend, modify, or otherwise update any other information in the Original Filing. Accordingly, this Amendment should be read in conjunction with the Original Filing and with our filings with the SEC subsequent to the filing of the Original Filing. In addition, this Amendment does not reflect events that may have occurred after the Original Filing Date. | | |
| Document Fiscal Year Focus | 2022 | | |
| Document Fiscal Period Focus | FY | | |
| Trading Symbol | ONCT | | |
| Current Fiscal Year End Date | --12-31 | | |
| Entity Filer Category | Non-accelerated Filer | | |
| Entity Well-known Seasoned Issuer | No | | |
| Entity Voluntary Filers | No | | |
| Entity Small Business | true | | |
| Entity Emerging Growth Company | false | | |
| Entity Current Reporting Status | Yes | | |
| Entity Shell Company | false | | |
| Entity Common Stock, Shares Outstanding | | 58,711,451 | |
| Entity Public Float | | | $ 52,700 |
| Entity File Number | 000-50549 | | |
| Entity Tax Identification Number | 62-1715807 | | |
| Entity Address, Address Line One | 12230 El Camino Real | | |
| Entity Address, Address Line Two | Suite 230 | | |
| Entity Address, City or Town | San Diego | | |
| Entity Address, State or Province | CA | | |
| Entity Address, Postal Zip Code | 92130 | | |
| City Area Code | 858 | | |
| Local Phone Number | 434-1113 | | |
| Entity Interactive Data Current | Yes | | |
| Title of 12(b) Security | Common Stock, par value $0.001 per share | | |
| Security Exchange Name | NASDAQ | | |
| Entity Incorporation, State or Country Code | DE | | |
| ICFR Auditor Attestation Flag | false | | |
| Document Annual Report | true | | |
| Document Transition Report | false | | |
| Documents Incorporated by Reference | DOCUMENTS INCORPORATED BY REFERENCE None | | |
| Auditor Name | BDO USA, LLP | | |
| Auditor Location | San Diego, California | | |
| Auditor Firm ID | 243 | | |
