XML 57 R48.htm IDEA: XBRL DOCUMENT
v3.22.1

Loans And Related Allowances For Loan Losses (TDRs) (Details) - contract | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2022 | Dec. 31, 2021
Troubled Debt Restructuring [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Number of contracts | 12 | 12

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

X
- Definition Number of financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LoanRestructuringModificationAxis=func_TroubledDebtRestructuringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |