XML 67 R60.htm IDEA: XBRL DOCUMENT
v3.25.2

Borrowings - Schedule of Federal Home Loan Bank Advances by Branch of FHLB Bank (Detail) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Principal Amounts | $ 58,953 | $ 52,268
Federal Home Loan Bank Advances One [Member] |  |
Principal Amounts | $ 7,205 | $ 520
Maturity Dates | 2025 | 2025
Interest Rates | 4.49% | 0.00%
Federal Home Loan Bank Advances Two [Member] |  |
Principal Amounts | $ 50,000 | $ 50,000
Maturity Dates | 2026 | 2026
Federal Home Loan Bank Advances Three [Member] |  |
Principal Amounts | $ 718 | $ 718
Maturity Dates | 2028 | 2028
Interest Rates | 0.00% | 0.00%
Federal Home Loan Bank Advances Four [Member] |  |
Principal Amounts | $ 400 | $ 400
Maturity Dates | 2029 | 2029
Interest Rates | 0.00% | 0.00%
Federal Home Loan Bank Advances Five [Member] |  |
Principal Amounts | $ 200 | $ 200
Maturity Dates | 2030 | 2030
Interest Rates | 0.00% | 0.00%
Federal Home Loan Bank Advances Six [Member] |  |
Principal Amounts | $ 430 | $ 430
Maturity Dates | 2031 | 2031
Interest Rates | 0.00% | 0.00%
Minimum [Member] | Federal Home Loan Bank Advances Two [Member] |  |
Interest Rates | 4.38% | 4.38%
Maximum [Member] | Federal Home Loan Bank Advances Two [Member] |  |
Interest Rates | 4.75% | 4.75%

X
- Definition Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 470 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478878/942-470-45-1 + Details
Name: | us-gaap_AdvancesFromFederalHomeLoanBanks
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The year of maturity, when only one maturity date applies, for the advances from the Federal Home Loan Bank as of the Balance Sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 470 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478878/942-470-45-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477734/942-470-50-3 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresDueDate
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:gYearListItemType
Balance Type: | na
Period Type: | instant

X
- Definition States the interest rate applicable to Federal Home Loan Bank advances outstanding as of the Balance Sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 470 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478878/942-470-45-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477734/942-470-50-3 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | fsea_FederalHomeLoanBankAdvancesAxis=fsea_FederalHomeLoanBankAdvancesOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsea_FederalHomeLoanBankAdvancesAxis=fsea_FederalHomeLoanBankAdvancesTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsea_FederalHomeLoanBankAdvancesAxis=fsea_FederalHomeLoanBankAdvancesThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsea_FederalHomeLoanBankAdvancesAxis=fsea_FederalHomeLoanBankAdvancesFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsea_FederalHomeLoanBankAdvancesAxis=fsea_FederalHomeLoanBankAdvancesFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsea_FederalHomeLoanBankAdvancesAxis=fsea_FederalHomeLoanBankAdvancesSixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |