Percentage Of Amount Borrowed.

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Share based compensation arrangement by share based payment award equity instruments other than options grants in period grant date fair value.

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Stock Repurchase During Period Shares Esop

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The amount of plan compensation cost recognized during the period.

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Fair value of unearned shares held by the employee stock ownership plan (ESOP).

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The shares that, although not legally released, will be released by a future scheduled and committed debt service payment and will be allocated to employees for service rendered in the current accounting period. The ESOP documents typically define the period of service to which the shares relate. ESOP shares are released to compensate employees directly, to settle employer liabilities for other employee benefits, and to replace dividends on allocated shares that are used for debt service.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt classified as noncurrent. Excludes lease obligation.

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Amount of noncash expense for share-based payment arrangement.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Stock Based Compensation - Additional Information (Detail) - USD ($)						3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 18, 2024	Nov. 18, 2023	Jun. 01, 2023	May 25, 2023	Nov. 18, 2021	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares committed to be released each year, ESOP						11,517		11,517		15,354
Unearned compensation for ESOP						$ 3,927,000		$ 3,927,000		$ 4,348,000
Stock options granted, outstanding								249,144		249,144
Share price			$ 7.99							$ 7.99
Share based expense recognized						102,000	$ 102,000	$ 306,000	$ 298,000
Income tax (benefit) expense						640,000	427,000	$ 176,000	667,000
Weighted average future recognition period								1 month 6 days		10 months 24 days
Restricted stock awards granted			2,478							2,478
Fair value related to grant			$ 20,000
Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock awards time-vest	50.00%	50.00%
Restricted Stock Awards [Member] \| Directors and Members [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award,					98,850
Share price								$ 11.95
Total fair value related to stock options granted								$ 1,200,000
Minimum [Member] \| Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issued stock option granted, term								3 years
2021 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unearned compensation for ESOP						44,000		$ 44,000		$ 350,000
Common stock shares issued during period, new issues								348,801
Issued stock option granted, term								10 years
Stock options granted, outstanding				249,144
Income tax (benefit) expense						27,000	27,000	$ 81,000	80,000
2021 Equity Incentive Plan [Member] \| Director [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unearned compensation for ESOP						411,000		411,000		$ 598,000
Share based expense recognized						62,000	67,000	187,000	88,000
Income tax (benefit) expense						$ 16,000	18,000	$ 50,000	24,000
Weighted average future recognition period								1 year 7 months 6 days		2 years 4 months 24 days
2021 Equity Incentive Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Payment Arrangement, Exercise of Option								249,144
Stock Issued During Period, Shares, Restricted Stock Award,								99,657
First Seacoast Bank Employee Stock Ownership Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares committed to be released each year, ESOP						15,354		15,354
Employee stock option compensation recognized						$ 35,000	$ 29,000	$ 103,000	$ 99,000
Unearned compensation for ESOP						3,900,000		3,900,000		$ 4,000,000
Employee stock option unallocated share fair value						3,200,000		$ 3,200,000		2,800,000
Employee stock option plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock repurchase								423,715
Percentage of purchase price common stock								100.00%
Remaining principal balance of debt						$ 4,200,000		$ 4,200,000		$ 4,200,000