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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -Premises and Equipment and Wealth Management and Group Fee Income (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Assets under management	$ 2,212.0	$ 2,242.0
Chemung Financial Corporation
Property, Plant and Equipment [Line Items]
Assets under management	$ 301.9	$ 381.3
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	15 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	50 years
Equipment and Furniture | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	3 years
Equipment and Furniture | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	10 years

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- Definition

The carrying amount of assets an investment adviser manages on behalf of investors.

+ References

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- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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