XML 61 R49.htm IDEA: XBRL DOCUMENT v3.24.2.u1

LOANS AND ALLOWANCE FOR CREDIT LOSSES - Modifications (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 440	$ 1,920	$ 440	$ 2,195
Residential Mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 440		$ 440
% of Loan Class	0.16%		0.16%
Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis		$ 1,920		$ 2,195
% of Loan Class		0.21%		0.24%
Weighted-average interest rate reduction	0.00%	0.00%	0.00%	0.00%
Weighted-average term extension	0 months	0 months	0 months	60 months
Weighted-average payment delay	6 months	4 months	6 months	4 months
Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 0	$ 0	$ 0	$ 0
Principal Forgiveness | Residential Mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0		0
Principal Forgiveness | Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis		0		0
Principal Reduction	0	0	0	0
Contractual Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0	0	0	0
Contractual Interest Rate Reduction | Residential Mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0		0
Contractual Interest Rate Reduction | Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis		0		0
Extended Maturity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0	0	0	275
Extended Maturity | Residential Mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0		0
Extended Maturity | Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis		0		275
Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	440	1,920	440	1,920
Payment Deferral | Residential Mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	440		440
Payment Deferral | Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis		1,920		1,920
Combination
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0	0	0	0
Combination | Residential Mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 0		$ 0
Combination | Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis		$ 0		$ 0

X

- Definition

Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount

+ References

No definition available.

+ Details

Name:	chmg_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount
Namespace Prefix:	chmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Financing Receivable, Excluding Accrued Interest, Modified in Period, Payment Delay

+ References

No definition available.

+ Details

Name:	chmg_FinancingReceivableExcludingAccruedInterestModifiedInPeriodPaymentDelay
Namespace Prefix:	chmg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Financing Receivable, Excluding Accrued Interest, Modified in Period, Term Extension

+ References

No definition available.

+ Details

Name:	chmg_FinancingReceivableExcludingAccruedInterestModifiedInPeriodTermExtension
Namespace Prefix:	chmg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage

+ References

No definition available.

+ Details

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

X

- Definition

Accumulated amortized cost excluding accrued interest, of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestModifiedAccumulated
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

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

X

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PrincipalForgivenessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ContractualInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PaymentDeferralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=chmg_CombinationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: