| Document and Entity Information Document | Apr. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 12, 2021 |
| Entity Registrant Name | StepStone Group Inc. |
| Entity Central Index Key | 0001796022 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39510 |
| Entity Tax Identification Number | 84-3868757 |
| Entity Address, Address Line One | 450 Lexington Avenue, 31st Floor |
| Entity Address, City or Town | New York, |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10017 |
| City Area Code | 212 |
| Local Phone Number | 351-6100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A common stock, par value $0.001 per share |
| Trading Symbol | STEP |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
