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Paycheck Protection Program Loans pledged as collateral for borrowings under the Paycheck Protection Program Liquidity Facility of the FRB.

No definition available.

Name:	unb_PaycheckProtectionProgramLoansPledgedAsCollateral
Namespace Prefix:	unb_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Number of loans outstanding under the SBA Paycheck Protection Program as part of the CARES Act.

No definition available.

Name:	unb_PaycheckProtectionProgramNumberOfLoans
Namespace Prefix:	unb_
Data Type:	xbrli:integerItemType
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Origination fee to be collected related to loans outstanding under the SBA Paycheck Protection Program as part of the CARES Act.

No definition available.

Name:	unb_PaycheckProtectionProgramOriginationFee
Namespace Prefix:	unb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Origination fee recognized in income on loans advanced under the SBA Paycheck Protection Program as part of the CARES Act.

No definition available.

Name:	unb_PaycheckProtectionProgramOriginationFeeRecognized
Namespace Prefix:	unb_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Total dollar amount of loans outstanding under the SBA Paycheck Protection Program as part of the CARES Act.

No definition available.

Name:	unb_PaycheckProtectionProgramTotalAmountOfLoansOutstanding
Namespace Prefix:	unb_
Data Type:	xbrli:monetaryItemType
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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.

No definition available.

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
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Data Type:	xbrli:stringItemType
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Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18794-111554

Name:	us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans
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Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5086-111524

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Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL49126937-111524