| **Employee Benefit Plans (Matching Retirement/Savings Plan) (Details) (USD $)**                  | 12 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended |
|--------------------------------------------------------------------------------------------------|-----------------|----------------|-----------------|----------------|-----------------|
||
| **Defined Contribution Pension and Other Postretirement Plans Disclosure [Line Items]**          |            |           |            |           |            |   |   |   |   |   |   |   |   |
| Employer matching contribution percentage                                                        | 50.00%          |           |            | 50.00%         |            | 50.00% |   |   | 50.00% |   |   |   |   |
| Percentage of pay deferred by employee eligible for employer matching contributions              | 6.00%           |           |            | 6.00%          |            | 6.00% |   |   | 6.00% |   |   |   |   |
| Discretionary contributions                                                                      |            |           |            |           |            | $ 0 | $ 0 | $ 0 |   |   |   |   |   |
| Matching and discretionary contributions                                                         | $ 500,000       | $ 600,000      | $ 400,000       |           |            | $ 500,000 | $ 600,000 | $ 400,000 |   | $ 0 | $ 0 | $ 0 | $ 0 |
| Non-tax qualified profit-sharing supplemental executive retirement plan, remaining balances paid |            |           |            |           | 2               |   |   |   |   |   |   |   |   |

| X                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Deferred Compensation Arrangement with Individual, Number of Balances Paid
+ References
No definition available.
+ Details**Name:**cob_DeferredCompensationArrangementwithIndividualNumberofBalancesPaid**Namespace Prefix:**cob_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**cob_DefinedContributionPensionAndOtherPostretirementPlansDisclosureLineItems**Namespace Prefix:**cob_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of the cost recognized during the period for defined contribution plans.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942
+ Details**Name:**us-gaap_DefinedContributionPlanCostRecognized**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of discretionary contributions made by an employer to a defined contribution plan.
+ References
No definition available.
+ Details**Name:**us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.
+ References
No definition available.
+ Details**Name:**us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage employer matches of the employee's percentage contribution matched.
+ References
No definition available.
+ Details**Name:**us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |