LOANS AND ALLOWANCE FOR LOAN LOSSES, Troubled Debt Restructuring by Portfolio Segment (Details) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	0	1
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 0	$ 163
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	186
Allowance Related to Troubled Debt Restructurings assigned during period	$ 0	$ 39
Residential Real Estate [Member] \| Interest Rate and Maturity Concession [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	0	1
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 0	$ 163
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	186
Allowance Related to Troubled Debt Restructurings assigned during period	$ 0	$ 39

Allowance Related to Troubled Debt Restructurings assigned during period

No definition available.

Name:	cac_AllowanceRelatedtoTroubledDebtRestructuringsassignedduringperiod
Namespace Prefix:	cac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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