| Document and Entity Information Document | Sep. 30, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Sep. 30, 2021 |
| Entity Registrant Name | Renewable Energy Group, Inc. |
| Entity Central Index Key | 0001463258 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-35397 |
| Entity Tax Identification Number | 26-4785427 |
| Entity Address, Address Line One | 416 South Bell Avenue |
| Entity Address, City or Town | Ames |
| Entity Address, State or Province | IA |
| Entity Address, Postal Zip Code | 50010 |
| City Area Code | 515 |
| Local Phone Number | 239-8000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $.0001 per share |
| Trading Symbol | REGI |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
