XML 67 R57.htm IDEA: XBRL DOCUMENT v3.21.2

Fair Value of Financial Instruments (Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques) (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Measurements, Recurring [Member] | Investment Securities - Available for Sale [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	$ 16,230	$ 13,260
Fair value input, unobservable input value, description	LIBOR+ 3.75%	LIBOR+ 5.25%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Comparable Properties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	$ 2,099	$ 1,465
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member] | Market Comparable Properties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	$ 443	$ 913
Fair value measurements discount rate	15.00%	15.00%
Minimum [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Comparable Properties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurements discount rate	10.00%	10.00%
Maximum [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Comparable Properties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurements discount rate	15.00%	15.00%
Weighted Average [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Comparable Properties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurements discount rate	10.50%	12.50%

X

- Definition

Fair Value Input, Unobservable Input Value, Description

+ References

No definition available.

+ Details

Name:	func_FairValueInputUnobservableInputValueDescription
Namespace Prefix:	func_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair Value Measurements Discount Rate

+ References

No definition available.

+ Details

Name:	func_FairValueMeasurementsDiscountRate
Namespace Prefix:	func_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=func_InvestmentSecuritiesAvailableForSaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ValuationTechniqueAxis=func_DiscountedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=func_ImpairedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ValuationTechniqueAxis=func_MarketComparablePropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=func_OtherRealEstateOwnedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: