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Fair Value of Financial Instruments (Narrative) (Details) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 USD ($) security | Dec. 31, 2019 USD ($)
Fair Value of Financial Instruments [Abstract] |  |
Acquired trust preferred securities, number of securities | security | 9 |
Trust preferred securities, amortized cost | $ 18,500 |
Trust preferred securities, fair value | 13,300 |
Fair value, assets, level 1 to level 2 transfers, amount | $ 0 | $ 0

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- Definition Acquired Trust Preferred Securities, Number of Securities + References No definition available. + Details
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- Definition Amortized cost of preferred stocks issued by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures. + References No definition available. + Details
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Namespace Prefix: | func_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Fair Value of preferred stocks issued by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures. + References No definition available. + Details
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Namespace Prefix: | func_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- References No definition available. + Details
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