Percentage of Common stock repurchase

No definition available.

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- Definition

It represents the number of treasury stock shares outstanding.

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
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Period Type:	instant

- Definition

Vested restricted stock award surrendered in lieu of a cash payment.

+ References

No definition available.

+ Details

Name:	fsea_VestedRestrictedStockAwardSurrenderedInLieuOfACashPayment
Namespace Prefix:	fsea_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

+ Details

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Period Type:	instant

- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

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Period Type:	instant

- Details

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- Details

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Namespace Prefix:
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- Details

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Treasury Stock - Additional Information (Detail) - shares	Jun. 30, 2023	Dec. 31, 2022	Nov. 18, 2022	Sep. 23, 2020
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