| **Income Taxes**                     | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              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| **Income Tax Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              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| Income Taxes                         | Income TaxesThe components of income tax expense for the years ended December 31 are as follows: (dollars in thousands) 2014 2013 2012Current:      Federal $— $— $—State — — —Total current taxes — — —Deferred      Federal 3,714 21,276 (13,709)State 537 14,628 (2,722)Total deferred taxes 4,251 35,904 (16,431)Increase (decrease) in valuation allowance (146,743) (34,578) 15,392Total income tax (benefit) expense - continuing operations $(142,492) $1,326 $(1,039)A reconciliation of income tax expense computed at the statutory federal income tax rate to actual income tax expense is presented in the following table as of December 31: (dollars in thousands)        2014 2013 2012Amount of tax computed using Federal statutory tax rate of 35% in all years $2,788 $(55) $(14,365)Increases (decreases) resulting from effects of:      Non-taxable income (54) (88) (169)State income taxes, net of federal benefit 349 9,508 (1,769)Valuation allowance on deferred tax assets (146,743) (34,578) 15,392Bank-owned life insurance (403) (375) —Reduction of deferred tax assets at Granite  — 28,293 —Other 1,571 (1,379) (128)Total income tax (benefit) expense - continuing operations $(142,492) $1,326 $(1,039)The components of deferred tax assets and liabilities and the tax effect of each are as follows: (dollars in thousands) December 31, 2014 December 31, 2013Deferred tax assets:    Allowance for loan losses $8,037 $10,364Net operating loss 137,412 135,050Compensation and benefit plans 1,277 995Fair value basis on securities 656 919Pension and other post-retirement benefits 1,470 1,080Other real estate owned 2,256 4,090Gross unrealized securities losses 2,560 10,215Interest on nonperforming loans — 1,339Other 851 529Subtotal deferred tax assets 154,519 164,581Less: Valuation allowance (1,300) (148,043)Total deferred tax assets 153,219 16,538Deferred tax liabilities:    Core deposit intangible 1,513 2,051Depreciable basis of premises and equipment 563 495Net deferred loan fees and costs 1,306 1,077Gross unrealized securities gains 490 1,249Fair value basis of loans 2,473 951Other 441 500Total deferred tax liabilities 6,786 6,323Net deferred tax assets $146,433 $10,215As of December 31, 2014 and December 31, 2013, net deferred income tax assets totaling $146.4 million and $10.2 million, respectively, are recorded on COB’s balance sheet. In 2013 the Company’s gross deferred tax assets were offset by a valuation allowance of $148.0 million. During 2014 management reevaluated the continuing need for this allowance in accordance with the procedures described in the “Income Taxes” section of  Note 1 and as more fully described below, and applied its judgment to determine that it is more likely than not that all but $1.3 million of the Company’s deferred tax assets will be realized.The Company’s deferred tax assets consist primarily of consolidated federal and Bank-originated North Carolina loss carryforwards from prior periods. The consolidated federal net operating loss carryforwards are $355.9 million and $349.6 million and the North Carolina net economic loss carryforwards are $371.8 million and $365.8 million at December 31, 2014 and 2013, respectively. The remaining federal and North Carolina carryforward periods range between fifteen and nineteen years and fourteen and ten years, respectively, at December 31, 2014.Management regularly evaluates the likelihood that the Company will be able to realize its deferred tax assets and the continuing need for a valuation allowance. In 2013 and prior years management determined that sufficient evidence was not available to conclude that it was more likely than not that all of its deferred tax assets could be realized, requiring a valuation allowance for certain of its deferred tax assets.  At December 31, 2014 management determined, based on all available positive and negative evidence, that it is more likely than not that future taxable income will be available during the carryforward periods to absorb all of the consolidated federal net operating loss carryforward and all but a small portion of the Bank’s North Carolina net economic loss carryforward.  As a result of this determination, $142.5 million of valuation allowance against the Company's deferred tax assets was reversed. A number of factors played a critical role in this determination, including:•Improvements in the asset quality of the loan portfolio and diminishment of credit-related losses that were the source of the Company's losses; •Implementation of strong internal controls making it unlikely that the large volume of troubled loans leading to the Company’s losses between 2008 and 2012 will reoccur;•The increased remoteness and diminished relevance of such losses;•Continued improvement of the Company’s financial metrics and six consecutive quarters of earnings;•A credible forecast of future taxable income based on management’s demonstrated forecasting accuracy;•Various cost-reduction initiatives that will have a continuing positive effect on earnings in future periods;•Availability of tax planning strategies, and •Long-dated carryforward periods.Accordingly, upon consideration of all available objectively verifiable positive and negative evidence, management has applied its judgment to conclude that the Company’s valuation allowance should be reduced from $148.0 million at December 31, 2013 to $1.3 million at December 31, 2014.Management will continue to regularly assess the Company’s ability to realize its deferred tax assets. Changes in earnings performance and future earnings projections may, among other factors, require the Company to adjust its valuation allowance, which would impact the Company's income tax expense in the period of adjustment.Under GAAP, COB is not required to provide a deferred tax liability for the tax effect of additions to the tax bad debt reserve accumulating through 1987. Retained earnings at December 31, 2014 include approximately $5.0 million for which no provision for federal income tax has been made. In the remote possibility that circumstances occur requiring a reduction of the reserve such reduction could be taxable and subject to the then-current corporate income tax rate.The merger of COB and Granite Corp. in 2011 resulted in an ownership change for Granite Corp. under Internal Revenue Code Section 382 and the Regulations thereunder. Accordingly, the Company is required to apply a limitation against Granite Corp.’s pre-acquisition net operating loss carryforwards and net unrealized built-in losses. During 2013, COB determined that it would be able to use only $2.9 million of the Granite Corp. net operating loss carryforwards and built in losses and reduced both its deferred tax asset and related valuation allowance by $28.3 million.The State of North Carolina passed legislation to reduce the income tax rates from 6.9% to 6.0% in 2014 and to 5.0% in 2015. The DTA has been reduced by $5.3 million to account for the reduction in income tax rates to 5%. The net reduction in DTA is offset by a corresponding reduction in the valuation allowance. |

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| - Definition
The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.
+ References
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