| Document and Entity Information | Feb. 16, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | This Current Report on Form 8-K/A amends the Current Report on Form 8-K that was filed with the Securities and Exchange Commission on February 16, 2021 (the “Initial Form 8-K”) by Malvern Bancorp, Inc. (the “Company”). The primary purpose of this Current Report on Form 8-K/A is to further disclose the involvement of both the Audit Committee (as defined below) and Baker Tilly (as defined below) in the determinations, and the date of such determinations, referenced in the Initial Form 8-K with respect to the non-reliance on previously issued financial statements, as set forth in more detail below. |
| Document Period End Date | Feb. 16, 2021 |
| Entity Registrant Name | Malvern Bancorp, Inc. |
| Entity Central Index Key | 0001550603 |
| Entity Emerging Growth Company | false |
| Entity File Number | 000-54835 |
| Entity Incorporation, State or Country Code | PA |
| Entity Tax Identification Number | 45-5307782 |
| Entity Address, Address Line One | 42 E. 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 |
