Loans - Summary of Composition of Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified
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Dec. 31, 2014
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Dec. 31, 2013
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
$ 1,331,366us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |
$ 1,264,763us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |
Construction and Land Development [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
22,744us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_ConstructionAndLandDevelopmentMember |
33,058us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_ConstructionAndLandDevelopmentMember |
Commercial and Industrial [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
149,732us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_CommercialAndIndustrialPortfolioSegmentMember |
76,675us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_CommercialAndIndustrialPortfolioSegmentMember |
Commercial Real Estate [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
696,272us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
696,317us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Residential Portfolio Segment [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
257,305us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
286,041us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Consumer Portfolio Segment [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
10,925us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
8,824us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Home Equity [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
151,275us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_HomeEquityPortfolioSegmentMember |
130,277us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_HomeEquityPortfolioSegmentMember |
Overdrafts [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
1,263us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_OverdraftsMember |
834us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cnbka_OverdraftsMember |
Municipal [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Total |
$ 41,850us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_InvestmentTypeAxis = us-gaap_MunicipalNotesMember |
$ 32,737us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_InvestmentTypeAxis = us-gaap_MunicipalNotesMember |