| Cover - USD ($) | 12 Months Ended | ||
| Dec. 31, 2021 | Mar. 01, 2022 | Jun. 30, 2021 | |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | false | ||
| Document Annual Report | true | ||
| Document Transition Report | false | ||
| Document Period End Date | Dec. 31, 2021 | ||
| Document Fiscal Period Focus | FY | ||
| Document Fiscal Year Focus | 2021 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity File Number | 001-36020 | ||
| Entity Registrant Name | Onconova Therapeutics, Inc. | ||
| Entity Central Index Key | 0001130598 | ||
| Entity Tax Identification Number | 22-3627252 | ||
| Entity Incorporation, State or Country Code | DE | ||
| Entity Address, Address Line One | 12 Penns Trail | ||
| Entity Address, City or Town | Newtown | ||
| Entity Address, State or Province | PA | ||
| Entity Address, Postal Zip Code | 18940 | ||
| City Area Code | 267 | ||
| Local Phone Number | 759-3680 | ||
| Title of 12(b) Security | Common Stock, par value $.01 per share | ||
| Trading Symbol | ONTX | ||
| Security Exchange Name | NASDAQ | ||
| Entity Well-known Seasoned Issuer | No | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Non-accelerated Filer | ||
| Entity Small Business | true | ||
| Entity Emerging Growth Company | false | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 109 | ||
| Entity Common Stock, Shares Outstanding | 20,895,563 | ||
| ICFR Auditor Attestation Flag | true | ||
| Auditor Name | Ernst & Young LLP | ||
| Auditor Location | Philadelphia, PA | ||
| Auditor Firm ID | 42 |
