| **Shareholders' Equity (Preferred Stock) (Details) (USD $)**                        | 0 Months Ended | 12 Months Ended |
|-------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Class of Stock [Line Items]**                                                     |           |            |   |   |
| Reverse stock split, conversion ratio                                               | 0.01           |            | 0.01 | 0.01 |
| Preferred stock, shares outstanding                                                 |           |            | 0 |   |
| Unpaid cumulative dividends                                                         |           | $ 0             | $ 0 |   |
| **Impact of preferred stock activity on the Consolidated Statement of Operations:** |           |            |   |   |
| Gain on retirement of preferred stock                                               |           | 0               | 0 | 9,375,000 |
| Preferred stock gain on retirement, net of accretion, and dividends                 |           | 0               | 0 | 44,592,000 |
| Preferred stock [Member]                                                            |           |            |   |   |
| **Impact of preferred stock activity on the Consolidated Statement of Operations:** |           |            |   |   |
| Gain on retirement of preferred stock                                               |           | 0               | 0 | 48,000,000 |
| Dividends and accretion on preferred stock                                          |           | 0               | 0 | (3,408,000) |
| Series A Preferred stock [Member]                                                   |           |            |   |   |
| **Class of Stock [Line Items]**                                                     |           |            |   |   |
| Preferred stock, shares outstanding                                                 |           | 0               | 0 |   |
| Dividends and deferred interest paid                                                |           |            |   | 4,500,000 |
| Accretion of discount on preferred stock                                            |           |            |   | 600,000 |
| **Impact of preferred stock activity on the Consolidated Statement of Operations:** |           |            |   |   |
| Gain on retirement of preferred stock                                               |           | 0               | 0 | 38,625,000 |
| Dividends and accretion on preferred stock                                          |           | 0               | 0 | (2,652,000) |
| Preferred stock [Member]                                                            |           |            |   |   |
| **Class of Stock [Line Items]**                                                     |           |            |   |   |
| Preferred stock, shares outstanding                                                 |           | 0               | 0 |   |
| **Impact of preferred stock activity on the Consolidated Statement of Operations:** |           |            |   |   |
| Gain on retirement of preferred stock                                               |           | 0               | 0 | 9,375,000 |
| Dividends and accretion on preferred stock                                          |           | $ 0             | $ 0 | $ (756,000) |

| X                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Gain on repurchase and retirement of preferred stock.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Preferred Stock Dividends and Accretion of Redemption Discount
+ References
No definition available.
+ Details**Name:**cob_PreferredStockDividendsAndAccretionOfRedemptionDiscount**Namespace Prefix:**cob_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585
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| X                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of accretion of the preferred stock redemption discount during the period.
+ References
No definition available.
+ Details**Name:**us-gaap_PreferredStockAccretionOfRedemptionDiscount**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Aggregate amount of cumulative preferred dividends in arrears.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644
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| X                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of preferred stock dividends that is an adjustment to net income apportioned to common stockholders.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.28) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Stock Split -URI http://asc.fasb.org/extlink&oid=6525746Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB TOPIC 4.C) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770
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