| Document and Entity Information Document - shares | 3 Months Ended | |
| Mar. 31, 2021 | Apr. 30, 2021 | |
| Cover [Abstract] | ||
| Document Type | 10-Q/A | |
| Document Quarterly Report | true | |
| Document Period End Date | Mar. 31, 2021 | |
| Document Transition Report | false | |
| Entity File Number | 001-39050 | |
| Entity Registrant Name | OPORTUN FINANCIAL CORPORATION | |
| Entity Incorporation, State or Country Code | DE | |
| Entity Tax Identification Number | 45-3361983 | |
| Entity Address, Address Line One | 2 Circle Star Way | |
| Entity Address, City or Town | San Carlos, | |
| Entity Address, State or Province | CA | |
| Entity Address, Postal Zip Code | 94070 | |
| City Area Code | 650 | |
| Local Phone Number | 810-8823 | |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share | |
| Trading Symbol | OPRT | |
| Security Exchange Name | NASDAQ | |
| Entity Current Reporting Status | Yes | |
| Entity Interactive Data Current | Yes | |
| Entity Filer Category | Accelerated Filer | |
| Entity Small Business | true | |
| Entity Emerging Growth Company | false | |
| Entity Shell Company | false | |
| Entity Common Stock, Shares Outstanding | 27,979,915 | |
| Current Fiscal Year End Date | --12-31 | |
| Document Fiscal Year Focus | 2021 | |
| Document Fiscal Period Focus | Q1 | |
| Entity Central Index Key | 0001538716 | |
| Amendment Flag | true | |
| Amendment Description | Oportun Financial Corporation (the "Company") is filing this Amendment No. 1 (the “Amendment”) to its Quarterly Report on Form 10-Q for the quarter ended March 31, 2021, as filed with the Securities and Exchange Commission on May 7, 2021 (the “Original Form 10-Q”) in order to correct an inadvertent omission of certain language in paragraph 4 of each of the Section 302 certifications filed as Exhibits 31.1 and 31.2 to the Original Form 10-Q (the “Section 302 Certifications”). Management has, and at the date of the Original Form 10-Q had, designed internal control over financial reporting to provide reasonable assurance regarding the reliability of financial reporting and the preparation of the Company’s financial statements in accordance with generally accepted accounting principles.The Amendment should be read in conjunction with the Original Form 10-Q and does not modify or update the Original Form 10-Q other than as set forth in the Amendment. The Amendment does not reflect events occurring after the filing of the Original Form 10-Q other than the correction of the Section 302 Certifications. |
