v3.25.3

Portfolio Loans Receivable and Allowance for Credit Losses - Schedule of Loan Modifications to Borrowers Experiencing Financial Difficulty (Details) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 loanModification | Sep. 30, 2024 loanModification | Sep. 30, 2025 USD ($) loanModification | Sep. 30, 2024 USD ($) loanModification
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Number of loan modifications | loanModification | 0 | 0 | 1 | 4
Amortized Cost Basis |  |  | $ 44 | $ 963
Residential | Real estate: | Extended Maturity and Interest Rate Reduction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Amortized Cost Basis |  |  |  | $ 760
% of Total Loan Type |  |  |  | 0.199%
Term increase to the life of the loan after loan modifications |  |  |  | 1 year
Contractual interest rate before loan modifications |  | 8.375% |  | 8.375%
Contractual interest rate loan modifications |  | 6.375% |  | 6.375%
Residential | Residential - Home Equity | Extended Maturity and Interest Rate Reduction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Amortized Cost Basis |  |  |  | $ 91
% of Total Loan Type |  |  |  | 0.164%
Term increase to the life of the loan after loan modifications |  |  |  | 22 years
Contractual interest rate before loan modifications |  | 10.49% |  | 10.49%
Contractual interest rate loan modifications |  | 6.375% |  | 6.375%
Commercial and Industrial | Extended Maturity and Interest Rate Reduction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Amortized Cost Basis |  |  | $ 44 |
% of Total Loan Type |  |  | 0.007% |
Commercial and Industrial | Contractual Interest Rate Reduction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Amortized Cost Basis |  |  |  | $ 112
% of Total Loan Type |  |  |  | 0.044%
Contractual interest rate before loan modifications |  | 11.25% |  | 11.25%
Contractual interest rate loan modifications |  | 6.00% |  | 6.00%
Commercial and Industrial | Payment Deferral |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Payment deferral period after loan modifications |  | 6 months |  | 6 months

X
- Definition Financing Receivable, Excluding Accrued Interest, Modified In Period, Number Of Contracts + References No definition available. + Details
Name: | cbnk_FinancingReceivableExcludingAccruedInterestModifiedInPeriodNumberOfContracts
Namespace Prefix: | cbnk_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty. + References 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

X
- Definition Percentage, excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables. + References 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_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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 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 Reference 2: 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 3: 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 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

X
- Definition Period of payment deferral of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -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 2: 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_FinancingReceivableModifiedPaymentDeferralPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage, after modification, of weighted-average interest rate of financing receivable 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 Reference 2: 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 + Details
Name: | us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateAfterModification
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage, before modification, of weighted-average interest rate of financing receivable 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 Reference 2: 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 + Details
Name: | us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateBeforeModification
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- 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 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_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityAndInterestRateReductionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=cbnk_CommercialAndIndustrialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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