Deposit (Schedule of deposit liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Non-interest bearing deposits	$ 468,554	$ 506,613
Non-Interest bearing deposits, percentage	30.00%	32.00%
Interest bearing deposits	$ 1,122,731	$ 1,064,120
Total deposits	$ 1,591,285	$ 1,570,733
Non-Interest and Interest bearing deposits, percentage	100.00%	100.00%
Demand Deposit Liability [Member]
Interest bearing deposits	$ 362,585	$ 327,685
Interest bearing deposits, percentage	23.00%	21.00%
Money Market Liability [Member]
Interest bearing deposits	$ 339,163	$ 365,192
Interest bearing deposits, percentage	21.00%	23.00%
Savings Deposit Liability [Member]
Interest bearing deposits	$ 242,441	$ 250,720
Interest bearing deposits, percentage	15.00%	16.00%
Time Deposit Retail Liability [Member]
Interest bearing deposits	$ 117,461	$ 120,523
Interest bearing deposits, percentage	7.00%	8.00%
Time Deposit Brokered Liability [Member]
Interest bearing deposits	$ 61,081
Interest bearing deposits, percentage	4.00%	0.00%

Percentage of aggregate liabilities related to interest bearing deposits.

No definition available.

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- Definition

Percentage of aggregate liabilities related to non-interest and interest bearing deposits.

+ References

No definition available.

+ Details

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- Definition

Percentage of aggregate liabilities related to non interest bearing deposits.

+ References

No definition available.

+ Details

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Namespace Prefix:	func_
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- Definition

The aggregate of all domestic interest-bearing and noninterest-bearing deposit liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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- Definition

Total amount of interest-bearing domestic deposit liabilities, which may include brokered, retail, demand, checking, notice of withdrawal, money market and other interest-bearing deposits.

+ References

+ Details

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- Definition

Amount of domestic noninterest-bearing deposits held by the entity, which may include demand deposits, checking, brokered and retail deposits.

+ References

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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