Parent Company Financial Information - Schedule of condensed statements of financial condition (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
ASSETS
Cash on deposit at the Bank	$ 8,117	$ 11,102
Investment in the Bank	28,053	157,620
Equity securities	2,258
Other assets	5,988	4,204
TOTAL ASSETS	879,952	822,408
LIABILITIES
Accrued and other liabilities	5,704	5,341
TOTAL LIABILITIES	687,626	605,482
Commitments and contingencies
STOCKHOLDERS' EQUITY
Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued
Common stock, $0.01 par value, 150,000,000 shares authorized; 14,896,590 shares issued and outstanding at June 30, 2022 and 15,170,566 shares issued and outstanding at June 30, 2021	149	152
Additional paid-in capital	159,546	168,349
Unearned common stock held by employee stock ownership plan	(9,599)	(10,004)
Retained earnings	57,587	58,493
Accumulated other comprehensive loss	(15,357)	(64)
TOTAL WILLIAM PENN BANCORPORATION STOCKHOLDERS' EQUITY	192,326	216,926	$ 96,365
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	879,952	822,408
Parent Company
ASSETS
Cash on deposit at the Bank	41,301	57,995
Investment in the Bank	148,364	158,857
Equity securities	2,258
Other assets	551	103
TOTAL ASSETS	192,474	216,955
LIABILITIES
Accrued and other liabilities	148	29
TOTAL LIABILITIES	148	29
Commitments and contingencies
STOCKHOLDERS' EQUITY
Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued
Common stock, $0.01 par value, 150,000,000 shares authorized; 14,896,590 shares issued and outstanding at June 30, 2022 and 15,170,566 shares issued and outstanding at June 30, 2021	149	152
Additional paid-in capital	159,546	168,349
Unearned common stock held by employee stock ownership plan	(9,599)	(10,004)
Retained earnings	57,587	58,493
Accumulated other comprehensive loss	(15,357)	(64)
TOTAL WILLIAM PENN BANCORPORATION STOCKHOLDERS' EQUITY	192,326	216,926
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 192,474	$ 216,955