Loans and Allowance for Credit Losses on Loans - TDR (Details) $ in Thousands	12 Months Ended
Dec. 31, 2024 USD ($) loan	Dec. 31, 2023 USD ($) loan
Financing Receivable, Modifications [Line Items]
Total % of Portfolio	0.00%	0.10%
Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0	$ 0
Financing Receivable, Modifications, Number of Contracts \| loan	3	1
Payment Deferral
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0	$ 0
Extended Maturity
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	1,060	4,494
Interest Rate Concession
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0	0
Extended Maturity and Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0	0
Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0	$ 0
Commercial real estate \| Commercial real estate, non owner-occupied
Financing Receivable, Modifications [Line Items]
Total % of Portfolio		0.30%
Commercial real estate \| Commercial real estate, non owner-occupied \| Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount		$ 0
Financing Receivable, Modifications, Number of Contracts \| loan		1
Commercial real estate \| Commercial real estate, non owner-occupied \| Payment Deferral
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount		$ 0
Commercial real estate \| Commercial real estate, non owner-occupied \| Extended Maturity
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount		$ 4,494
Weighted Average Term Extension (Years)		1 year 3 months 18 days
Commercial real estate \| Commercial real estate, non owner-occupied \| Interest Rate Concession
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount		$ 0
Weighted Average Interest Rate Reduction		0.00%
Commercial real estate \| Commercial real estate, non owner-occupied \| Extended Maturity and Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount		$ 0
Commercial real estate \| Commercial real estate, non owner-occupied \| Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount		$ 0
Commercial
Financing Receivable, Modifications [Line Items]
Total % of Portfolio	0.30%
Commercial \| Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0
Financing Receivable, Modifications, Number of Contracts \| loan	3
Commercial \| Payment Deferral
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0
Commercial \| Extended Maturity
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	1,060
Commercial \| Interest Rate Concession
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0
Commercial \| Extended Maturity and Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0
Commercial \| Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0
Commercial \| Commercial \| Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0
Commercial \| Commercial \| Extended Maturity
Financing Receivable, Modifications [Line Items]
Weighted Average Term Extension (Years)	1 year 4 months 24 days
Commercial \| Commercial \| Interest Rate Concession
Financing Receivable, Modifications [Line Items]
Weighted Average Interest Rate Reduction	0.00%

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Percentage, excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ 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/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

+ Details

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

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityAndInterestRateReductionMember
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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cac_CommercialRealEstatePortfolioSegmentNonOwnerOccupiedMember
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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: