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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

+ Details

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

+ Details

Name:	us-gaap_LegalFees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=chmg_FixedInterestRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=chmg_VariableInterestRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	srt_LitigationCaseAxis=chmg_Fanev.ChemungCanalTrustCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands		3 Months Ended
	Jun. 15, 2018	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Commitments to make loans \| Fixed Rate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet contractual amounts of financial instruments			$ 11,520	$ 9,137
Commitments to make loans \| Variable Rate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet contractual amounts of financial instruments			21,741	18,033
Unused lines of credit \| Fixed Rate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet contractual amounts of financial instruments			442	848
Unused lines of credit \| Variable Rate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet contractual amounts of financial instruments			219,178	212,601
Standby letters of credit \| Fixed Rate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet contractual amounts of financial instruments			0	0
Standby letters of credit \| Variable Rate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet contractual amounts of financial instruments			$ 16,241	$ 16,161
Fane v. Chemung Canal Trust Company
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Amount awarded to other party	$ 3,300
Legal reserve					$ 2,300
Legal fees		$ 1,000