XML 124 R107.htm IDEA: XBRL DOCUMENT
v3.24.0.1

COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |
Allowance for credit losses on unfunded commitments | $ 22,517 | [1] | $ 19,659 | [1] | $ 21,025
Contingent obligations | 11,300 |  |  |  |
Unfunded Loan Commitment |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |
Allowance for credit losses on unfunded commitments | $ 919 |  | $ 0 |  | $ 0
Minimum | Fixed Rate |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |
Interest rate on fixed-rate commitments to make loans | 5.75% |  |  |  |
Maturity period of fixed-rate commitments to make loans (years) | 7 years |  |  |  |
Commitments period to make fixed-rate commercial draw notes (months) | 3 months |  |  |  |
Interest rate on fixed-rate commitments to make commercial draw notes (in hundredths) | 2.79% |  |  |  |
Maximum |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |
Commitments period to make real estate and home equity loans (days) | 60 days |  |  |  |
Off-balance sheet financial instruments, standard term | 12 months |  |  |  |
Maximum | Fixed Rate |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |
Interest rate on fixed-rate commitments to make loans | 8.13% |  |  |  |
Maturity period of fixed-rate commitments to make loans (years) | 30 years |  |  |  |
Commitments period to make fixed-rate commercial draw notes (months) | 24 months |  |  |  |
Interest rate on fixed-rate commitments to make commercial draw notes (in hundredths) | 8.17% |  |  |  |
[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 Represents the period, for which commitments are generally made to make commercial draw notes. + References No definition available. + Details
Name: | chmg_CommitmentsPeriodToMakeCommercialDrawNotes
Namespace Prefix: | chmg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the period, for which commitments are generally made to make real estate and home equity loans. + References No definition available. + Details
Name: | chmg_CommitmentsPeriodToMakeRealEstateAndHomeEquityLoans
Namespace Prefix: | chmg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition For off-balance sheet financial instruments, the standard term for the agreement. + References No definition available. + Details
Name: | chmg_FairValueOffBalanceSheetRisksFinancialInstrumentStandardTerm
Namespace Prefix: | chmg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Refer to interest rate on fixed-rate commitments to make commercial draw notes. + References No definition available. + Details
Name: | chmg_InterestRateOnFixedRateCommitmentsToMakeCommercialDrawNotes
Namespace Prefix: | chmg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Refer to interest rate on the fixed-rate commitments to make loans. + References No definition available. + Details
Name: | chmg_InterestRateOnFixedRateCommitmentsToMakeLoans
Namespace Prefix: | chmg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Refers to maturity period of the fixed-rate commitments to make loans. + References No definition available. + Details
Name: | chmg_MaturityPeriodOfFixedRateCommitmentsToMakeLoans
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_FairValueOffBalanceSheetRisksDisclosureInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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 Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483076/450-20-50-1 Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483076/450-20-50-10 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_UnfundedLoanCommitmentMember
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: | chmg_InterestRateTypeAxis=chmg_FixedInterestRateMember
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: |