| Document and Entity Information | Sep. 14, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 14, 2021 |
| Entity Registrant Name | GREENSKY, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38506 |
| Entity Tax Identification Number | 82-2135346 |
| Entity Address, Address Line One | 5565 Glenridge Connector |
| Entity Address, Address Line Two | Suite 700 |
| Entity Address, City or Town | Atlanta |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30342 |
| City Area Code | 678 |
| Local Phone Number | 264-6105 |
| Written Communications | true |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001712923 |
| Title of 12(b) Security | Class A common stock, $0.01 par value |
| Trading Symbol | GSKY |
| Security Exchange Name | NASDAQ |
