XML 92 R76.htm IDEA: XBRL DOCUMENT
v3.8.0.1

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands |  | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Mar. 23, 2016 USD ($) | Jun. 30, 2017 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Mar. 26, 2016 USD ($) Proceeding Party | Dec. 31, 2015 USD ($) | Jun. 30, 2016 USD ($) | Sep. 30, 2014 USD ($)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contingent obligations |  |  | $ 15,000 |  |  |  |  |
Legal accruals and settlements |  |  | $ 850 | $ 1,200 |  | $ 0 |  |
Settled Litigation |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contingent obligations |  |  |  |  |  |  |  | $ 4,300
Claims settled and dismissed | Proceeding |  |  |  |  | 2 |  |  |
Number of party | Party |  |  |  |  | 2 |  |  |
Litigation settlement amount |  |  |  |  | $ 12,100 |  |  |
Insurance proceeds |  |  |  |  | $ 7,900 |  |  |
Pending Litigation |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contingent obligations |  | $ 2,300 |  |  |  |  | $ 1,200 |
Damages sought | $ 4,000 |  |  |  |  |  |  |
Loss contingency, accrual, noncurrent |  | 850 |  |  |  |  |  |
Legal accruals and settlements |  | $ 200 |  |  |  |  |  |
Minimum |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Commitments period to make fixed-rate commercial draw notes |  |  | 3 months |  |  |  |  |
Minimum | Fixed Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Interest rate on fixed-rate commitments to make loans |  |  | 3.375% |  |  |  |  |
Maturity period of fixed-rate commitments to make loans |  |  | 5 years |  |  |  |  |
Interest rate on fixed-rate commitments to make commercial draw notes (in hundredths) |  |  | 4.25% |  |  |  |  |
Maximum |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Commitments period to make real estate and home equity loans |  |  | 60 days |  |  |  |  |
Commitments period to make fixed-rate commercial draw notes |  |  | 24 months |  |  |  |  |
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 |  |  | 5.875% |  |  |  |  |
Maturity period of fixed-rate commitments to make loans |  |  | 30 years |  |  |  |  |
Interest rate on fixed-rate commitments to make commercial draw notes (in hundredths) |  |  | 5.50% |  |  |  |  |
Commitments to make loans | Fixed Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contractual amounts of financial instruments with off-balance sheet risk |  |  | $ 16,019 | 38,246 |  |  |  |
Commitments to make loans | Variable Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contractual amounts of financial instruments with off-balance sheet risk |  |  | 28,591 | 33,189 |  |  |  |
Unused lines of credit | Fixed Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contractual amounts of financial instruments with off-balance sheet risk |  |  | 1,604 | 610 |  |  |  |
Unused lines of credit | Variable Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contractual amounts of financial instruments with off-balance sheet risk |  |  | 200,353 | 208,124 |  |  |  |
Standby letters of credit | Fixed Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contractual amounts of financial instruments with off-balance sheet risk |  |  | 0 | 0 |  |  |  |
Standby letters of credit | Variable Rate |  |  |  |  |  |  |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |  |  |  |  |  |  |
Contractual amounts of financial instruments with off-balance sheet risk |  |  | $ 15,022 | $ 14,241 |  |  |  |

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: | num: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: | num: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 Represents the number of parties involved in transaction. + References No definition available. + Details
Name: | chmg_NumberOfParty
Namespace Prefix: | chmg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 + Details
Name: | us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_FairValueOffBalanceSheetRisksDisclosureInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.3) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_LegalFees
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount awarded to other party in judgment or settlement of litigation. + References No definition available. + Details
Name: | us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of loss contingency liability expected to be resolved after one year or beyond the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 + Details
Name: | us-gaap_LossContingencyAccrualCarryingValueNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The number of claims settled and dismissed during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349 + Details
Name: | us-gaap_LossContingencyClaimsSettledAndDismissedNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The value (monetary amount) of the award the plaintiff seeks in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349 + Details
Name: | us-gaap_LossContingencyDamagesSoughtValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of insurance proceeds for an event or transaction that is unusual in nature or infrequent in occurrence, or both. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64828382&loc=d3e15138-107781 + Details
Name: | us-gaap_UnusualOrInfrequentItemInsuranceProceeds
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_LitigationStatusAxis=us-gaap_SettledLitigationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_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: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommitmentsToExtendCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | chmg_InterestRateTypeAxis=chmg_VariableInterestRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_UnusedLinesOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |