| Document and Entity Information | Oct. 14, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | FRANKLIN RESOURCES INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000038777 |
| Document Type | 8-K |
| Document Period End Date | Oct. 14, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-09318 |
| Entity Tax Identification Number | 13-2670991 |
| Entity Address, Address Line One | One Franklin Parkway |
| Entity Address, City or Town | San Mateo |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94403 |
| City Area Code | (650) |
| Local Phone Number | 312-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.10 per share |
| Trading Symbol | BEN |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
