| Document And Entity Information | 12 Months Ended |
| Jan. 30, 2020 | |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Jan. 30, 2020 |
| Entity Registrant Name | TFS FINANCIAL CORPORATION |
| Entity Incorporation, State or Country Code | X1 |
| Entity File Number | 001-33390 |
| Entity Tax Identification Number | 52-2054948 |
| Entity Address, Address Line One | 7007 Broadway Ave., |
| Entity Address, City or Town | Cleveland, |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 44105 |
| City Area Code | (216) |
| Local Phone Number | 441-6000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | TFSL |
| Security Exchange Name | NASDAQ |
| Entity Central Index Key | 0001381668 |
| Amendment Flag | false |
