XML 72 R60.htm IDEA: XBRL DOCUMENT v3.24.2.u1

FAIR VALUE - Level 3 Non-Recurring Fair Value Measurement (Details) - Non-recurring - Fair Value, Inputs, Level 3 - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Commercial and industrial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 13	$ 64
Commercial and industrial | Discounted cash flow | Minimum | Market discount rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	42.00%	47.30%
Commercial and industrial | Discounted cash flow | Maximum | Market discount rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	42.00%	56.80%
Commercial and industrial | Discounted cash flow | Weighted Average | Market discount rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	42.00%	54.80%
Other real estate owned:
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 546	$ 327
Other real estate owned: | Residential mortgages | Sales comparison
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 228	$ 116
Other real estate owned: | Residential mortgages | Sales comparison | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	20.80%	20.80%
Other real estate owned: | Residential mortgages | Sales comparison | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	20.80%	20.80%
Other real estate owned: | Residential mortgages | Sales comparison | Weighted Average
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	20.80%	20.80%
Other real estate owned: | Home equity lines and loans | Sales comparison
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 318	$ 211
Other real estate owned: | Home equity lines and loans | Sales comparison | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	20.80%	20.80%
Other real estate owned: | Home equity lines and loans | Sales comparison | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	20.80%	20.80%
Other real estate owned: | Home equity lines and loans | Sales comparison | Weighted Average
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value inputs, discount to appraised value	20.80%	20.80%

X

- Definition

Fair Value Inputs, Discount To Appraised Value

+ References

No definition available.

+ Details

Name:	chmg_FairValueInputsDiscountToAppraisedValue
Namespace Prefix:	chmg_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair value portion of asset recognized for present right to economic benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueDiscountedCashFlowMember
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:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
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:

X

- Details

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

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: