Federal Home Loan Bank, Advances, Amount Restructured

No definition available.

Name:	cob_FederalHomeLoanBankAdvancesAmountRestructured
Namespace Prefix:	cob_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Federal Home Loan Bank, Advances, General Debt Obligations, Amount of Available, Unused Funds, by Pledging Additional Collateral

+ References

No definition available.

+ Details

Name:	cob_FederalHomeLoanBankAdvancesGeneralDebtObligationsAmountOfAvailableUnusedFundsByPledgingAdditionalCollateral
Namespace Prefix:	cob_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Federal Home Loan Bank, Advances, General Debt Obligations, Amount of Available, Unused Funds, No Additional Collateral Pledged

+ References

No definition available.

+ Details

Name:	cob_FederalHomeLoanBankAdvancesGeneralDebtObligationsAmountOfAvailableUnusedFundsNoAdditionalCollateralPledged
Namespace Prefix:	cob_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

States the interest rate applicable to Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

+ References

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

States the lowest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateRangeFrom
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

States the highest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateRangeTo
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64702-112823

+ Details

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

- Details

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

- Definition

Amount of federal home loan bank advances maturing after the fifth fiscal year following the latest fiscal year.

+ References

+ Details

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

- Definition

Amount of federal home loan bank advances maturing in the fifth fiscal year following the latest fiscal year.

+ References

+ Details

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

- Definition

Amount of federal home loan bank advances maturing in the second fiscal year following the latest fiscal year.

+ References

+ Details

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

- Definition

Amount of federal home loan bank advances maturing in the fourth fiscal year following the latest fiscal year.

+ References

+ Details

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

- Definition

Amount of federal home loan bank advances maturing in the third fiscal year following the latest fiscal year.

+ References

+ Details

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

- Definition

Amount of federal home loan bank advances maturing in the next fiscal year following the latest fiscal year.

+ References

+ Details

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

- Details

Name:	dei_LegalEntityAxis=cob_CommunityoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingAugust272018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingDecember292014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingJune152020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingSeptember272016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingSeptember272017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingSeptember272018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cob_FederalHomeLoanBankAdvancesMaturingSeptember82015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Short-Term Borrowings and Long-Term Debt (FHLB Advances) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2013
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	$ 68,234,000	$ 73,283,000
FHLB Advances, interest rate, ranging from	0.93%	0.93%
FHLB Advances, interest rate, ranging to	6.15%	6.15%
Scheduled Maturities of FHLB Advances
2015	3,000,000
2016	5,000,000
2017	5,000,000
2018	5,234,000
2019	0
2020 and thereafter	50,000,000
FHLB advances	68,234,000	73,283,000
FHLB advances restructured			50,000,000
FHLB Advances, Maturing December 29, 2014 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	0	5,000,000
Scheduled Maturities of FHLB Advances
FHLB advances	0	5,000,000
FHLB Advances, interest rate	3.3125%
FHLB Advances, Maturing September 8, 2015 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	3,000,000	3,000,000
Scheduled Maturities of FHLB Advances
FHLB advances	3,000,000	3,000,000
FHLB Advances, interest rate	3.71%
FHLB Advances, Maturing September 27, 2016 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	5,000,000	5,000,000
Scheduled Maturities of FHLB Advances
FHLB advances	5,000,000	5,000,000
FHLB Advances, interest rate	0.93%
FHLB Advances, Maturing September 27, 2017 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	5,000,000	5,000,000
Scheduled Maturities of FHLB Advances
FHLB advances	5,000,000	5,000,000
FHLB Advances, interest rate	1.42%
FHLB Advances, Maturing August 27, 2018 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	234,000	283,000
Scheduled Maturities of FHLB Advances
FHLB advances	234,000	283,000
FHLB Advances, interest rate	6.15%
FHLB Advances, Maturing September 27, 2018 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	5,000,000	5,000,000
Scheduled Maturities of FHLB Advances
FHLB advances	5,000,000	5,000,000
FHLB Advances, interest rate	1.84%
FHLB Advances, Maturing June 15, 2020 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB advances	50,000,000	50,000,000
Scheduled Maturities of FHLB Advances
FHLB advances	50,000,000	50,000,000
FHLB Advances, interest rate	1.6224%
CommunityOne [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB Advances, available borrowing capacity without pledging additional collateral	130,800,000
FHLB Advances, additional borrowing by pledging additional collateral	$ 202,500,000