Deposits (Deposit Composition) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deposits, by Component, Alternative [Abstract]
Noninterest-bearing demand deposits	$ 323,776	$ 290,461
Interest-bearing demand deposits	358,162	347,791
Savings deposits	86,349	80,507
Money market deposits	437,821	447,672
Brokered deposits	37,673	29,219
Time deposits less than $250,000	500,672us-gaap_TimeDepositsLessThan100000	517,687us-gaap_TimeDepositsLessThan100000
Time deposits $250,000 or more	49,967	35,368
Total deposits	$ 1,794,420us-gaap_Deposits	$ 1,748,705us-gaap_Deposits
Noninterest-bearing demand deposits, Percentage	18.04%	16.61%
Interest-bearing demand deposits, Percentage	19.96%	19.89%
Savings deposits, Percentage	4.81%	4.61%
Money market deposits, Percentage	24.40%	25.60%
Brokered deposits, Percentage	2.10%	1.67%
Time deposits less than $250,000, Percentage	27.90%	29.60%
Time deposits $250,000 or more, Percentage	2.79%	2.02%
Total deposits, Percentage	100.00%cob_PercentageOfDeposits	100.00%cob_PercentageOfDeposits

Percentage of Deposits

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- Definition

Percentage of Noninterest-bearing Domestic Deposits to Deposits, Demand

+ References

No definition available.

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- Definition

Percentage of Time Deposits, Less than 100000 to Deposits

+ References

No definition available.

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- Definition

Percentage of Time Deposits, More than 100000 to Deposits

+ References

No definition available.

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- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

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- Definition

Amount of interest-bearing domestic third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

+ References

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- Definition

Amount of money in interest-bearing domestic accounts that entitle the depositor to withdraw funds at any time without prior notice, also known as demand deposits.

+ References

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- Definition

Amount of interest-bearing domestic money market demand account deposit liabilities.

+ References

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- Definition

Amount of interest-bearing domestic savings deposit liabilities. Saving deposits bear interest and have no stated maturity.

+ References

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- Definition

Amount of money in noninterest-bearing domestic accounts that entitle the depositor to withdraw funds at any time without prior notice, also known as demand deposits.

+ References

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- Definition

Percentage of interest-bearing domestic brokered deposit liabilities to total deposit liabilities.

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No definition available.

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Percentage of interest-bearing domestic demand deposit liabilities to total deposit liabilities.

+ References

No definition available.

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- Definition

Percentage of interest-bearing domestic money market demand account deposit liabilities to total deposit liabilities.

+ References

No definition available.

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- Definition

Percentage of interest-bearing domestic savings deposit liabilities to total deposit liabilities.

+ References

No definition available.

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- Definition

The aggregate amount of domestic time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 405

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6479006&loc=d3e64164-112818

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- Definition

The aggregate amount of domestic or foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000.

+ References

No definition available.

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