LOANS AND ALLOWANCE FOR LOAN LOSSES (Troubled Debt Restructuring Loans) (Details) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 loan	Dec. 31, 2018 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	27		31
Recorded Investment	$ 4,117		$ 4,406
Specific Reserve	$ 533		$ 628
Number of Contracts \| loan	0	1
Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	22		25
Recorded Investment	$ 3,342		$ 3,614
Specific Reserve	$ 381		$ 443
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	2		2
Recorded Investment	$ 343		$ 347
Specific Reserve	$ 27		$ 23
Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	2		2
Recorded Investment	$ 133		$ 141
Specific Reserve	$ 0		$ 0
Consumer
Financing Receivable, Modifications [Line Items]
Number of Contracts \| loan	1		2
Recorded Investment	$ 299		$ 304
Specific Reserve	$ 125		$ 162

Allowance for Credit Losses, Related to Troubled Debt Restructured Loans

No definition available.

Name:	cac_AllowanceForCreditLossesRelatedToTroubledDebtRestructuredLoans
Namespace Prefix:	cac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Financing Receivable Modifications Number Of Contracts Outstanding

+ References

No definition available.

+ Details

Name:	cac_FinancingReceivableModificationsNumberOfContractsOutstanding
Namespace Prefix:	cac_
Data Type:	xbrli:integerItemType
Balance Type:	na
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_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

The amount of the outstanding recorded investment related to 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 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Details

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

- Details

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

- Details

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