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Treasury Stock - Additional Information (Detail) - shares | Jun. 30, 2023 | Dec. 31, 2022 | Nov. 18, 2022 | Sep. 23, 2020
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Equity Class Of Treasury Stock [Line Items] |  |  |  |
Vested restricted stock award surrendered in lieu of cash payment |  |  | 496 |
Treasury Stock, Shares outstanding | 114,899 | 114,899 |  |
Common Stock [Member] |  |  |  |
Equity Class Of Treasury Stock [Line Items] |  |  |  |
Percentage of repurchase of Common Stock |  |  |  | 2.20%
Number of shares authorized for repurchase |  | 114,403 |  |
Common Stock [Member] | Stockholders other than First Seacoast Bancorp, MHC [Member] |  |  |  |
Equity Class Of Treasury Stock [Line Items] |  |  |  |
Equity method investment ownership percentage |  |  |  | 5.00%
Common Stock [Member] | Maximum [Member] |  |  |  |
Equity Class Of Treasury Stock [Line Items] |  |  |  |
Number of shares authorized for repurchase |  |  |  | 114,403

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