| **Employee Benefit Plans (Assumed Benefit Obligations) (Details) (CommunityOne [Member], USD $)**             | 12 Months Ended |
|---------------------------------------------------------------------------------------------------------------|-----------------|
||
| Integrity Financial Corporation [Member] | Former president of acquiree [Member]                              |            |   |   |
| **Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]**                   |            |   |   |
| Benefit payments, payable period                                                                              | 10 years        |   |   |
| Provision expense for future benefits                                                                         | $ 17,000        | $ 39,000 | $ 49,000 |
| Payments made under provisions of the non-qualifying deferred compensation plan                               | 78,000          | 80,000 | 76,000 |
| Integrity Financial Corporation [Member] | Former president of acquiree [Member] | Other liabilities [Member] |            |   |   |
| **Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]**                   |            |   |   |
| Non-qualifying deferred compensation plan liability                                                           | 300,000         | 400,000 |   |
| Carolina Fincorp, Inc. [Member] | Retired executive of acquiree [Member]                                      |            |   |   |
| **Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]**                   |            |   |   |
| Benefit amount per year                                                                                       | $ 30,000        |   |   |
| Benefit payments, payable period                                                                              | 10 years        |   |   |

| X                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Deferred Compensation Arrangement with Individual, Annual Payment Amount
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Deferred Compensation Arrangement with Individual, Contractual Payable Period
+ References
No definition available.
+ Details**Name:**cob_DeferredCompensationArrangementWithIndividualContractualPayablePeriod**Namespace Prefix:**cob_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The compensation expense recognized during the period pertaining to the deferred compensation arrangement.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363
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| X                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of distributions made to the individual during the period.
+ References
No definition available.
+ Details**Name:**us-gaap_DeferredCompensationArrangementWithIndividualDistributionsPaid**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363
+ Details**Name:**us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |