XML 51 R41.htm IDEA: XBRL DOCUMENT
v3.23.2

Summary of Significant Accounting Policies - Additional Information (Detail) |  |  | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Jan. 19, 2023 $ / shares shares | Aug. 17, 2021 USD ($) | Jun. 30, 2023 USD ($) $ / shares shares | Jun. 30, 2022 USD ($) | Jun. 30, 2023 USD ($) Service Segment $ / shares shares | Jun. 30, 2022 USD ($) | Dec. 31, 2022 USD ($) $ / shares shares
Common stock, price per share | $ / shares |  |  | $ 0.01 |  | $ 0.01 |  | $ 0.01
Common stock issued | shares |  |  | 5,192,515 |  | 5,192,515 |  | 5,183,439
Number of core services | Service |  |  |  |  | 4 |  |
Number of reportable segment | Segment |  |  |  |  | 1 |  |
Accounts Purchase Price | $ |  | $ 324,000 |  |  |  |  |
Accounts Purchase Price, Paid | $ |  | $ 172,000 |  |  | $ 22,500,000 |  | $ 23,000,000
The Percentage of Accounts Receivables Paid To Seller |  | 85 |  |  |  |  |
Deposit Assets, Amortization Expense from Expirations | $ |  |  | $ 5,000 | $ 9,000 | $ 14,000 | $ 18,000 |
Emerging growth of company status |  |  |  |  | (i) the last day of the fiscal year of the Company during which it had total annual gross revenues of $1.07 billion (as adjusted for inflation) or more; (ii) the last day of the fiscal year of the Company following the fifth anniversary of the effective date of the Company’s initial public offering (which will be December 31, 2024 for the Company); (iii) the date on which the Company has, during the previous three-year period, issued more than $1.0 billion in non-convertible debt; or (iv) the date on which the Company is deemed to be a “large accelerated filer” under Securities and Exchange Commission regulations (generally, at least $700 million of voting and non-voting equity held by non-affiliates). |  |
First Seacoast Bancorp, Inc [Member] |  |  |  |  |  |  |
Common stock shares sold | shares | 2,805,000 |  |  |  |  |  |
Common stock, price per share | $ / shares | $ 10 |  |  |  |  |  |
Common stock coversion ratio | 0.8358 |  |  |  |  |  |
First Seacoast Bancorp, Inc [Member] | First Seacoast Bank Employee Stock Ownership Plan [Member] |  |  |  |  |  |  |
Common stock issued | shares | 224,400 |  |  |  |  |  |
ASU 2022-2 [Member] |  |  |  |  |  |  |
Change in accounting principle, accounting standards update, early adoption [true false] |  |  | true |  | true |  |
Change in accounting principle, accounting standards update, immaterial effect [true false] |  |  | true |  | true |  |
ASU 2019-11 [Member] |  |  |  |  |  |  |
Change in accounting principle, accounting standards update, early adoption [true false] |  |  | true |  | true |  |
Change in accounting principle, accounting standards update, immaterial effect [true false] |  |  | true |  | true |  |
ASU 2019-04 [Member] |  |  |  |  |  |  |
Change in accounting principle, accounting standards update, early adoption [true false] |  |  | true |  | true |  |
ASU 2016-13 [Member] |  |  |  |  |  |  |
Change in accounting principle, accounting standards update, early adoption [true false] |  |  | true |  | true |  |
Change in accounting principle, accounting standards update, immaterial effect [true false] |  |  | true |  | true |  |
Change in accounting principle, accounting standards update, adopted |  |  | true |  | true |  |
Change in accounting principle, accounting standards update, adoption date |  |  | Jan. 01, 2023 |  | Jan. 01, 2023 |  |

X
- Definition Common stock conversion ratio. + References No definition available. + Details
Name: | fsea_CommonStockConversionRatio
Namespace Prefix: | fsea_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents on satisfaction of any of these conditions entity can't enjoy it's emerging growth company status. + References No definition available. + Details
Name: | fsea_EmergingGrowthCompanyStatusClosingConditions
Namespace Prefix: | fsea_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of core services. + References No definition available. + Details
Name: | fsea_NumberOfCoreServices
Namespace Prefix: | fsea_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payments to acquire finance receivables paid. + References No definition available. + Details
Name: | fsea_PaymentsToAcquireFinanceReceivablesPaidAmount
Namespace Prefix: | fsea_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The percentage of accounts receivables paid to seller. + References No definition available. + Details
Name: | fsea_ThePercentageOfAccountsReceivablesPaidToSeller
Namespace Prefix: | fsea_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicates (true false) whether accounting standards update was adopted. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 405 -SubTopic 50 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147477123/405-50-65-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482477/820-10-65-13 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482477/820-10-65-13 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-5 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-5 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-6 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-6 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 832 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483482/832-10-65-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479845/805-20-65-3 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479845/805-20-65-3 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-2 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 848 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483550/848-10-65-2 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 105 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479343/105-10-65-6 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 105 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479343/105-10-65-6 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-4 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-4 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 8 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482615/740-10-65-8 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483194/926-20-65-2 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483194/926-20-65-2 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-6 Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-6 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481925/310-20-65-2 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481925/310-20-65-2 Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483443/250-10-50-1 Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-5 Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-5 Reference 34: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-2 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (a) -SubTopic 10 -Topic 326 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-3 Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (b) -SubTopic 10 -Topic 326 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-3 Reference 37: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (a) -SubTopic 10 -Topic 842 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-4 + Details
Name: | us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted
Namespace Prefix: | us-gaap_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | instant

X
- Definition Date accounting standards update was adopted, in YYYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 405 -SubTopic 50 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147477123/405-50-65-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482477/820-10-65-13 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482477/820-10-65-13 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-5 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-5 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-5 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-6 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-6 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-6 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 832 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483482/832-10-65-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479845/805-20-65-3 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479845/805-20-65-3 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479845/805-20-65-3 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-2 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 848 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483550/848-10-65-2 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 105 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479343/105-10-65-6 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 105 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479343/105-10-65-6 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-4 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-4 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 8 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482615/740-10-65-8 Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483194/926-20-65-2 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483194/926-20-65-2 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-6 Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-6 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 34: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481925/310-20-65-2 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481925/310-20-65-2 Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-5 Reference 37: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-5 Reference 38: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-2 Reference 39: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (a) -SubTopic 10 -Topic 326 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-3 Reference 40: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (b) -SubTopic 10 -Topic 326 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-3 Reference 41: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (a) -SubTopic 10 -Topic 842 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-4 Reference 42: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -SubTopic 10 -Topic 250 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483443/250-10-50-3 + Details
Name: | us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | instant

X
- Definition Indicates (true false) whether accounting standards update was early adopted. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 405 -SubTopic 50 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147477123/405-50-65-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482477/820-10-65-13 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482477/820-10-65-13 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-5 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-6 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 832 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483482/832-10-65-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479845/805-20-65-3 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-5 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-2 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 105 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479343/105-10-65-6 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-4 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 8 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482615/740-10-65-8 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483194/926-20-65-2 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-6 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 6 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-6 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480175/815-40-65-1 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481925/310-20-65-2 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483443/250-10-50-1 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480528/815-20-65-5 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482833/825-10-65-5 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-2 Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (a) -SubTopic 10 -Topic 842 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479832/842-10-65-4 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 3 -Subparagraph (c) -SubTopic 10 -Topic 326 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-3 + Details
Name: | us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateEarlyAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | instant

X
- Definition Indicates (true false) whether effect from applying amendment to accounting standards is immaterial. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483443/250-10-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 8 -Subparagraph (e)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482615/740-10-65-8 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 10 -Name Accounting Standards Codification -Section 65 -Paragraph 4 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479654/326-10-65-4 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (d)(1) -SubTopic 20 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481925/310-20-65-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480530/250-10-S99-3 + Details
Name: | us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect
Namespace Prefix: | us-gaap_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | instant

X
- Definition Face amount or stated value per share of common stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_CommonStockSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of amortization expense from expiration of contracts underlying deposit assets. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 340 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483054/340-30-50-2 + Details
Name: | us-gaap_DepositAssetsAmortizatonExpenseFromExpirations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482810/280-10-50-18 + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash outflow for the purchase of amounts due from customers, clients, lessees, borrowers, or others under the terms of its agreements therewith. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-13 + Details
Name: | us-gaap_PaymentsToAcquireFinanceReceivables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number of new stock issued during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481112/505-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481004/946-505-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(4)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(i)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_OwnershipAxis=fsea_FirstSeacoastBancorpIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis=fsea_FirstSeacoastBankEmployeeStockOwnershipPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate202202Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201911Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201904Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201613Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |