| **Basis of Presentation**                                                           | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   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| **Organization, Consolidation and Presentation of Financial Statements [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  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| Basis of Presentation                                                               | Basis of PresentationNature of OperationsCommunityOne Bancorp, ("COB" or the "Company," also referred to as “us” or “we” and our subsidiaries on a consolidated basis), is a bank holding company headquartered in Charlotte, North Carolina and  incorporated in 1984 under the laws of the State of North Carolina. Through our ownership of CommunityOne Bank, N.A. (the "Bank,") a national banking association founded in 1907 and headquartered in Asheboro, North Carolina, we offer a complete line of consumer, mortgage and business banking services, including loan, deposit and treasury management, as well as wealth management and trust services, to individual and small and middle market businesses through financial centers located throughout central, southern and western North Carolina.  Our strategy is to grow the Company organically by focusing on meeting the financial needs of customers in our market area by providing a suite of quality financial products and services through local and experienced bankers and lenders located in branches and loan production offices in our customers’ local markets.  We also offer the convenience of online and mobile banking capabilities. In addition to organic growth, our strategy is to grow through merger and acquisition activity in our markets, should attractive opportunities present themselves.  We define our market as communities located in North Carolina, as well as adjoining markets in South Carolina and Virginia.We earn revenue primarily from interest on loans and securities investments, mortgage banking income and fees charged for financial services provided to our customers.  Offsetting these revenues are the cost of deposits and other funding sources, provision for loan losses and operating costs such as salaries and employee benefits, occupancy, data processing expenses, loan origination and collection expenses and tax expense.GeneralIn the accompanying consolidated financial statements, prepared without audit, all significant intercompany balances and transactions have been eliminated.  Descriptions of the organization and business of COB, accounting policies followed by COB and other relevant information are contained in our Annual Report on Form 10-K for the year ended December 31, 2014 (the "Form 10-K"), including the Notes to the consolidated financial statements filed as part of that report.  This quarterly report should be read in conjunction with the Form 10-K.In the opinion of management, the accompanying consolidated financial statements contain the adjustments, all of which are normal recurring adjustments, necessary to present fairly the financial position of COB as of September 30, 2015 and December 31, 2014, and the results of its operations for the three and nine months ended and cash flows for the nine months ended September 30, 2015 and 2014, respectively.Use of EstimatesWe have made a number of estimates and assumptions relating to the reporting of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period to prepare these consolidated financial statements in conformity with accounting principles generally accepted in the United States ("GAAP").  Actual results could differ from those estimates.  Material estimates subject to change in the near term include, among other items, the allowance for loan losses (“ALL”), estimated cash flows of purchased impaired loans, the carrying value of other real estate owned ("OREO"), the carrying value of investment securities and the realization of deferred tax assets.ReclassificationCertain reclassifications have been made to the prior period consolidated financial statements to place them on a comparable basis with the current period consolidated financial statements.  These reclassifications have no effect on net income or shareholders' equity as previously reported.Recent Accounting PronouncementsIn January 2014, the FASB issued ASU No. 2014-04 Troubled Debt Restructurings by Creditors (Subtopic 310-40): "Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure" (“ASU No. 2014-04”). This pronouncement clarifies the criteria for concluding that an in substance repossession or foreclosure has occurred, and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan. The amendments also outline interim and annual disclosure requirements. The amendments became effective for the Company for interim and annual reporting periods beginning after December 15, 2014. These amendments did not have a material effect on the Company's financial statements.In May 2014, the FASB issued an update (ASU No. 2014-09, Revenue from Contracts with Customers) creating FASB Topic 606, Revenue from Contracts with Customers. The guidance in this update affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (for example, insurance contracts or lease contracts). The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance provides steps to follow to achieve the core principle. An entity should disclose sufficient information to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Qualitative and quantitative information is required about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The amendments in this update are effective for interim and annual reporting periods beginning after December 15, 2017. We are currently evaluating the impact of adopting the new guidance on the consolidated financial statements.In June 2014, the FASB issued ASU 2014-11, Transfers and Servicing (Topic 860): Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosures. The amendments in this ASU change the accounting for repurchase-to-maturity transactions and linked repurchase financings to secured borrowing accounting, which is consistent with the accounting for other repurchase agreements. The amendments also require two new disclosures. The first disclosure requires an entity to disclose information on transfers accounted for as sales in transactions that are economically similar to repurchase agreements. The second disclosure provides increased transparency about the types of collateral pledged in repurchase agreements and similar transactions accounted for as secured borrowings. The amendments became effective for the Company for interim and annual reporting periods beginning after December 15, 2014. These amendments did not have an impact on the Company’s consolidated financial statements, but resulted in additional disclosures. See Note 10 - Repurchase Agreement Borrowings.FASB - From time to time, the FASB issues exposure drafts for proposed statements of financial accounting standards. Such exposure drafts are subject to comment from the public, to revisions by the FASB and to final issuance by the FASB as statements of financial accounting standards. Management considers the effect of the proposed statements on the consolidated financial statements of COB and monitors the status of changes to and proposed effective dates of exposure drafts. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies are not expected to have a material impact on our financial position, results of operations or cash flows. |

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The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.
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