| **CommunityOne Bancorp (Parent Company)**                                        | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
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| **Condensed Financial Information of Parent Company Only Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| CommunityOne Bancrop (Parent Company)                                            | CommunityOne Bancorp (Parent Company)The parent company’s principal asset is its investment in its bank subsidiary, the Bank.The condensed financial position as of December 31, 2014 and 2013, and the condensed results of operations and cash flows for each of the years in the three-year period ended December 31, 2014 of COB, parent company only, are presented below. (dollars in thousands)        2014 2013  Condensed Balance Sheets      Assets:      Cash $6,032 $637  Investment in subsidiaries 322,615 143,683  Other assets 3,678 505  Total Assets $332,325 $144,825  Liabilities and shareholders’ equity:      Accrued liabilities $8,707 $7,762  Borrowed funds 56,702 56,702  Shareholders’ equity 266,916 80,361  Total Shareholders’ Equity and Liabilities $332,325 $144,825           2014 2013 2012Condensed Statements of Operations      Noninterest income $33 $31 $34Interest expense (1,146) (1,092) (1,157)Noninterest expense (1,011) (742) (970)Loss before tax (benefit) expense (2,124) (1,803) (2,093)Income tax expense (benefit) (3,180) — (311)Income (Loss) before equity in undistributed net loss of subsidiaries 1,056 (1,803) (1,782)Equity in undistributed net income (loss) of subsidiaries 149,402 320 (38,223)Net income (loss) $150,458 $(1,483) $(40,005)       Condensed Statements of Cash Flows 2014 2013 2012Cash flows from operating activities      Net Income (Loss) $150,458 $(1,483) $(40,005)Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:      Equity in undistributed net income (loss) of subsidiaries (149,402) (320) 38,223Other, net (2,095) 1,153 503Net cash used in operating activities (1,039) (650) (1,279)Cash flows from investing activities      Downstream cash investment in subsidiary (19,400) — (6,709)Net cash used in investing activities (19,400) — (6,709)Cash flows from financing activities      Proceeds from issuance of common stock, net of costs 24,982  6,694Other 852 681 (908)Net cash provided by financing activities 25,834 681 5,786Net increase (decrease) in cash 5,395 31 (2,202)Cash at beginning of period 637 606 2,808Cash at end of period $6,032 $637 $606 |

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| - Definition
The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 06 -Article 9Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=7656940&loc=d3e5283-111683Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 12Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph c -Article 5Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 05 -Paragraph c -Article 7
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