XML 81 R64.htm IDEA: XBRL DOCUMENT
v3.24.0.1

LOANS AND ALLOWANCE FOR CREDIT LOSSES - Narrative (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2023 USD ($) loan | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Accrued interest receivable on loans | $ 7,800,000 |  | $ 6,500,000 |  |
Residential mortgages held for sale | 0 |  | 0 |  |
Allowance for credit losses | 22,517,000 | [1] | 19,659,000 | [1] | $ 21,025,000
Loans individually analyzed | $ 8,035,000 |  | 7,482,000 |  |
Number of days past due after which a retail loan is rated | 90 days |  |  |  |
Collateral Pledged |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Allowance for credit losses | $ 267,000 |  |  |  |
Loans individually analyzed | 6,347,000 |  |  |  |
Residential Mortgages and Home Equity Loans | Asset Pledged as Collateral |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Financial instruments, owned, at fair value | 254,600,000 |  | 254,400,000 |  |
Commercial and Agricultural |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Allowance for credit losses | 5,055,000 |  | 3,373,000 |  | $ 3,591,000
Loans individually analyzed | $ 2,067,000 |  | $ 2,112,000 |  |
Commercial and Agricultural | Commercial and industrial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Number of contracts modified | loan | 1 |  |  |  |
Allowance for credit losses | $ 900,000 |  |  |  |
[1] | Effective January 1, 2023, the allowance calculation is based upon Current Expected Credit loss methodology. Prior to January 1, 2023, the allowance calculation was based upon incurred loss methodology. Refer to Note 1 for further discussion.

X
- Definition Financing Receivable Modifications Number Of Contracts1 + References No definition available. + Details
Name: | chmg_FinancingReceivableModificationsNumberOfContracts1
Namespace Prefix: | chmg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Days Past Due After Which A Loan Will Be Rated + References No definition available. + Details
Name: | chmg_NumberOfDaysPastDueAfterWhichALoanWillBeRated
Namespace Prefix: | chmg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481961/940-320-45-2 + Details
Name: | us-gaap_FinancialInstrumentsOwnedAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before allowance for credit loss, of accrued interest on financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-1 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11C -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-11C Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L(5)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480418/310-10-S99-4 + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481990/310-10-45-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 948 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481852/948-310-45-1 + Details
Name: | us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_CollateralAxis=us-gaap_CollateralPledgedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=chmg_ResidentialMortgagesAndHomeEquityLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PledgedStatusAxis=us-gaap_AssetPledgedAsCollateralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=chmg_CommercialAndAgriculturalPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_CommercialAndIndustrialSectorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |