| Cover | 12 Months Ended |
| Dec. 31, 2021 shares | |
| Entity Addresses [Line Items] | |
| Document Type | 20-F/A |
| Amendment Flag | false |
| Document Registration Statement | false |
| Document Annual Report | true |
| Document Transition Report | false |
| Document Shell Company 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 | 001-35147 |
| Entity Registrant Name | Renren Inc. |
| Entity Central Index Key | 0001509223 |
| Entity Incorporation, State or Country Code | E9 |
| Entity Address, Address Line One | 2828 N. Central Avenue Fl 7 |
| Entity Address, City or Town | Phoenix |
| Entity Address, State or Province | AZ |
| Entity Address, Country | US |
| Entity Address, Postal Zip Code | 85004 |
| 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 Emerging Growth Company | false |
| Document Accounting Standard | U.S. GAAP |
| Entity Shell Company | false |
| ICFR Auditor Attestation Flag | false |
| Auditor Name | Marcum Bernstein & Pinchuk LLP |
| Auditor Location | New York, NY |
| Auditor Firm ID | 5395 |
| ADR [Member] | |
| Entity Addresses [Line Items] | |
| Title of 12(b) Security | American depositary shares, each representing 45 Class A ordinary shares |
| Trading Symbol | RENN |
| Security Exchange Name | NYSE |
| Common Class A [Member] | |
| Entity Addresses [Line Items] | |
| Title of 12(b) Security | Class A ordinary shares, par value US$0.001 per share* |
| No Trading Symbol Flag | true |
| Security Exchange Name | NYSE |
| Entity Common Stock, Shares Outstanding | 815,936,577 |
| Common Class B [Member] | |
| Entity Addresses [Line Items] | |
| Entity Common Stock, Shares Outstanding | 305,388,450 |
| Business Contact [Member] | |
| Entity Addresses [Line Items] | |
| Entity Address, Address Line One | 2828 N. Central Avenue Fl 7 |
| Entity Address, City or Town | Phoenix |
| Entity Address, State or Province | AZ |
| Entity Address, Country | US |
| Entity Address, Postal Zip Code | 85004 |
| City Area Code | +1 |
| Local Phone Number | 833-258-7482 |
| Contact Personnel Name | Chris Palmer |
| Contact Personnel Email Address | ir@renren-inc.com |
