| Document and Entity Information | Mar. 10, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 10, 2021 |
| Entity Registrant Name | MALVERN BANCORP, INC. |
| Entity Central Index Key | 0001550603 |
| Entity Emerging Growth Company | false |
| Entity File Number | 000-54385 |
| Entity Incorporation, State or Country Code | PA |
| Entity Tax Identification Number | 45-5307782 |
| Entity Address, Address Line One | 42 East Lancaster Avenue |
| Entity Address, City or Town | Paoli |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19301 |
| City Area Code | 610 |
| Local Phone Number | 644-9400 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | MLVF |
| Security Exchange Name | NASDAQ |
