XML 89 R79.htm IDEA: XBRL DOCUMENT v3.23.3

Guarantees, Commitments and Contingencies - Summary of Commitment and Contingent Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Standby Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Commitments and contingent liabilities	$ 0	$ 0
Standby Performance Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Commitments and contingent liabilities	664	556
Commitments to Extend Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Commitments and contingent liabilities	$ 155,614	$ 186,169

X

- Definition

The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-10

+ Details

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- 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

Name:	us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=fusb_StandbyPerformanceLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=fusb_CommitmentsToExtendCredit1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: