Loans And Leases Receivable, Amortization Period

No definition available.

Name:	cbnk_LoansAndLeasesReceivableAmortizationPeriod
Namespace Prefix:	cbnk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans And Leases Receivable, Balloon Payment Period

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivableBalloonPaymentPeriod
Namespace Prefix:	cbnk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans And Leases Receivable, Covenant Compliance, Debt Service Coverage Ratio

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivableCovenantComplianceDebtServiceCoverageRatio
Namespace Prefix:	cbnk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans And Leases Receivable, Fixed Interest Rate Term

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivableFixedInterestRateTerm
Namespace Prefix:	cbnk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans And Leases Receivable, Initial Commitment Term

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivableInitialCommitmentTerm
Namespace Prefix:	cbnk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans And Leases Receivable, Percent Of Real Estate Portfolio

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivablePercentOfRealEstatePortfolio
Namespace Prefix:	cbnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Loans And Leases Receivable, Principal To Collateral Value Ratio, Percent

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivablePrincipalToCollateralValueRatioPercent
Namespace Prefix:	cbnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Loans And Leases Receivable, Repayment History Used For Scoring Model

+ References

No definition available.

+ Details

Name:	cbnk_LoansAndLeasesReceivableRepaymentHistoryUsedForScoringModel
Namespace Prefix:	cbnk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

+ Details

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

- Definition

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84165051&loc=d3e45377-112738

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159169&loc=d3e10152-111534

+ Details

Name:	us-gaap_LoansAndLeasesReceivableDeferredIncome
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_LoansAndLeasesReceivableDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

+ Details

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

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetReportedAmount
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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
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=cbnk_ConstructionPortfolioSegmentMember
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:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CreditCardReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=cbnk_SavingsDepositsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cbnk_OtherConsumerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=cbnk_OwnerOccupiedRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=cbnk_InvestorRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans Receivable - Classification of Loans (Details)	12 Months Ended
Loans Receivable - Classification of Loans (Details)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	$ 1,002,260,000	$ 889,011,000
Deferred origination fees, net	(1,992,000)	(1,591,000)
Allowance for loan losses	(11,308,000)	(10,033,000)	$ (8,597,000)
Loans receivable, net	988,960,000	877,387,000
Residential \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	407,844,000	342,684,000
Allowance for loan losses	(3,541,000)	(3,137,000)	(2,664,000)
Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	122,264,000	108,982,000
Allowance for loan losses	(1,578,000)	(1,497,000)	(1,174,000)
Commercial \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	278,691,000	259,853,000
Allowance for loan losses	$ (3,003,000)	(2,860,000)	(2,682,000)
Fixed interest rate term	5 years
Initial commitment term	10 years
Amortization period	25 years
Construction \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	$ 157,586,000	144,932,000
Allowance for loan losses	(2,093,000)	(1,646,000)	(1,591,000)
Consumer \| Credit card
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	34,673,000	31,507,000
Allowance for loan losses	(1,084,000)	(885,000)	(477,000)
Consumer \| Credit card \| Savings Deposits
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	$ 32,500,000	29,400,000
Repayment history used for scoring model	6 months
Consumer \| Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	$ 1,202,000	1,053,000
Allowance for loan losses	$ (9,000)	$ (8,000)	$ (9,000)
Minimum \| Construction \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Initial commitment term	12 months
Maximum \| Construction \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Initial commitment term	18 months
Owner Occupied Real Estate \| Residential \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Initial commitment term	30 years
Owner Occupied Real Estate \| Commercial \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable, gross	$ 129,100,000
Percent of real estate portfolio	46.00%
Owner Occupied Real Estate \| Construction \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Loan principal to collateral value ratio, percent	80.00%
Owner Occupied Real Estate \| Minimum \| Residential \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Fixed interest rate term	5 years
Owner Occupied Real Estate \| Maximum \| Residential \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Fixed interest rate term	7 years
Investor Real Estate \| Residential \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Initial commitment term	25 years
Balloon payment period	5 years
Covenant compliance, debt service coverage ratio	1.15
Investor Real Estate \| Construction \| Real estate:
Loans and Leases Receivable Disclosure [Line Items]
Loan principal to collateral value ratio, percent	75.00%