Deposit (Schedule of deposit liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Non-interest bearing deposits	$ 422,415	$ 426,737
Non-Interest bearing deposits, percentage	26.00%	27.00%
Interest bearing deposits	$ 1,201,159	$ 1,148,092
Total deposits	$ 1,623,574	$ 1,574,829
Non-Interest and Interest bearing deposits, percentage	100.00%	100.00%
Demand
Interest bearing deposits	$ 368,945	$ 386,803
Interest bearing deposits, percentage	23.00%	25.00%
Money market-retail
Interest bearing deposits	$ 465,504	$ 447,149
Interest bearing deposits, percentage	29.00%	28.00%
Money market-brokered
Interest bearing deposits	$ 2	$ 1
Interest bearing deposits, percentage	0.00%	0.00%
Savings deposits
Interest bearing deposits	$ 171,354	$ 170,972
Interest bearing deposits, percentage	10.00%	11.00%
Time deposits- retail
Interest bearing deposits	$ 145,354	$ 143,167
Interest bearing deposits, percentage	9.00%	9.00%
Time deposits- brokered
Interest bearing deposits	$ 50,000
Interest bearing deposits, percentage	3.00%

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_
Data Type:	dtr-types:percentItemType
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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
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(12))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ 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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- Details

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