| Cover | Apr. 23, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 23, 2021 |
| Entity File Number | 000-55084 |
| Entity Registrant Name | Prudential Bancorp, Inc. |
| Entity Central Index Key | 0001578776 |
| Entity Tax Identification Number | 46-2935427 |
| Entity Incorporation, State or Country Code | PA |
| Entity Address, Address Line One | 1834 West Oregon Avenue |
| Entity Address, City or Town | Philadelphia |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19145 |
| City Area Code | 215 |
| Local Phone Number | 755-1500 |
| 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 | PBIP |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
