XML 118 R107.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Segment Reporting - Additional Information (Details) |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 03, 2021 Branch | Sep. 30, 2021 Branch | Dec. 31, 2021 Segment
Segment Reporting Information [Line Items] |  |  |
Number of reportable segments | Segment |  |  | 2
ALC [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Number of office closed | Branch | 20 | 20 |

X
- Definition Represents number of office closed during period for restructuring and related cost. + References No definition available. + Details
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Namespace Prefix: | fusb_
Data Type: | xbrli:integerItemType
Balance Type: | na
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 -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8672-108599 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |