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Summary of Significant Accounting Policies (Details) $ / shares in Units, $ in Millions |  |  | 6 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Nov. 04, 2024 USD ($) $ / shares shares | Nov. 01, 2024 USD ($) $ / shares shares | Jun. 30, 2025 USD ($) | Sep. 30, 2024 nonbankSubsidiary segment $ / shares | Oct. 31, 2024 $ / shares | Dec. 31, 2023 $ / shares
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |  |
Number of nonbank subsidiaries | nonbankSubsidiary |  |  |  | 4 |  |
Number of reportable segments | segment |  |  |  | 1 |  |
Common stock, par value (in dollars per share) | $ / shares |  |  |  | $ 1.00 |  | $ 1.00
Subsequent Event |  |  |  |  |  |
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |  |
Net proceeds received after underwriting discount and other estimated offering expenses |  | $ 70.0 |  |  |  |
Number of shares issued in transaction (in shares) | shares | 2,375,000 | 2,375,000 |  |  |  |
Common stock, price per share (in dollars per share) | $ / shares | $ 29.50 | $ 29.50 |  |  |  |
Additional stock purchase, threshold trading days |  | 30 days |  |  |  |
Percentage of additional stock purchase |  | 15.00% |  |  |  |
Additional shares issued (in shares) | shares | 356,250 | 356,250 |  |  |  |
Proceeds of public offering, gross | $ 80.6 |  |  |  |  |
Proceeds of public offering, net | $ 76.5 |  |  |  |  |
Subsequent Event | William Penn Bancorporation |  |  |  |  |  |
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  |  |  | $ 0.01 |
Subsequent Event | William Penn Bancorporation |  |  |  |  |  |
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |  |
Recapitalization exchange ratio |  |  |  |  | 0.426 |
Subsequent Event | Scenario Forecast | William Penn Bancorporation |  |  |  |  |  |
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |  |
Consideration transferred |  |  | $ 127.0 |  |  |

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