| **Earnings Per Share**            | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| **Earnings Per Share [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Earnings Per Share                | Earnings Per ShareBasic net earnings per share, or basic earnings per share (“EPS”), is computed by dividing net income to common shareholders by the weighted average number of common shares outstanding for the period.Diluted EPS reflects the potential dilution that could occur if COB's potential common stock, which consists of dilutive stock options and a common stock warrant, were issued.  As required for entities with complex capital structures, a dual presentation of basic and diluted EPS is included on the face of the income statement, and a reconciliation of the numerator and denominator of the basic EPS computation to the numerator and denominator of the diluted EPS computation is provided in this note.(dollars in thousands, except share and per share data) For Three Months Ended  March 31, 2016 March 31, 2015Net income $3,914 $2,519Weighted average number of shares outstanding - basic 24,292,004 24,183,396Weighted average number of shares outstanding - diluted 24,314,112 24,195,108Net income per share - basic and diluted $0.16 $0.10During the three months ended March 31, 2016 and March 31, 2015, the price of the Company's common stock (as quoted on the Nasdaq Capital Market) was below the price of the common stock warrant.  As a result, the warrant is considered antidilutive and thus is not included in the diluted share calculation. For the three months ended March 31, 2016, there were an average of 500,540 antidilutive shares, while for the three months ended March 31, 2015, there were 22,127 antidilutive shares.  Of the antidilutive shares, the number of shares relating to stock options were 478,468 and 55 for the three months ended March 31, 2016, and March 31, 2015, respectively.  The number relating to the warrant was 22,072 for all periods presented. |

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| - Definition
The entire disclosure for earnings per share.
+ References
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