Goodwill and Identifiable Intangible Assets - Carrying Amount of Goodwill and Intangibles (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Intangible Assets And Goodwill [Line Items]
Goodwill, Beginning Balance	$ 2,714us-gaap_Goodwill	$ 2,714us-gaap_Goodwill
Goodwill, Ending Balance	2,714us-gaap_Goodwill	2,714us-gaap_Goodwill
Total, Beginning Balance	3,417	2,851
Additions	424	653
Amortization Expense	(186)	(87)
Total, Ending Balance	3,655	3,417
Mortgage Servicing Rights [Member]
Intangible Assets And Goodwill [Line Items]
Beginning Balance	703	137
Additions	424	653
Amortization Expense	(186)	(87)
Ending Balance	$ 941	$ 703

Aggregate amortization of intangible assets expense including goodwill.

No definition available.

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Balance Type:	debit
Period Type:	duration

- Definition

Intangible assets additions.

+ References

No definition available.

+ Details

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- Details

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- Definition

Intangible assets net including goodwill addition.

+ References

No definition available.

+ Details

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Namespace Prefix:	cnbka_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance.

+ References

No definition available.

+ Details

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- Definition

The net carrying amount as of the balance sheet date of other indefinite-lived and finite-lived intangible assets that are not separately presented on the statement of financial position.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Details

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