| **Loans and Allowance for Loan Losses (Tables)**                | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **Loans Receivable, Net [Abstract]**                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Loan Credit Quality Indicators                                  | The following table presents loans held for investment balances by risk grade as of September 30, 2013:(dollars in thousands) Pass Special Mention Substandard Doubtful    (Ratings 1-5) (Rating 6) (Rating 7) (Rating 8) TotalCommercial and agricultural $65,556 $640 $3,421 $— $69,617Real estate - construction 48,665 3,310 15,567 — 67,542Real estate - mortgage:          1-4 family residential 578,197 12,638 27,427 — 618,262Commercial 300,609 26,918 67,559 — 395,086Consumer 43,997 48 241 349 44,635Total $1,037,024 $43,554 $114,215 $349 $1,195,142The following table presents loans held for investment balances by risk grade as of December 31, 2012:(dollars in thousands) Pass Special Mention Substandard Doubtful    (Ratings 1-5) (Rating 6) (Rating 7) (Rating 8) TotalCommercial and agricultural $69,003 $3,447 $6,953 $301 $79,704Real estate - construction 40,117 2,031 16,266 — 58,414Real estate - mortgage:          1-4 family residential 504,819 15,855 32,625 239 553,538Commercial 296,271 50,275 95,126 164 441,836Consumer 42,495 178 426 444 43,543Total $952,705 $71,786 $151,396 $1,148 $1,177,035                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Past Due Loans                                                  | The following table presents an aging analysis of accruing and nonaccruing loans as of September 30, 2013:(dollars in thousands) Accruing          30-59 days past due 60-89 days past due More than 90 days past due Nonaccrual Total past due and nonaccrual Current and accruing Total LoansPC and Originated Loans              Commercial and agricultural $52 $— $— $590 $642 $57,558 $58,200Real estate - construction 47 — 76 10,190 10,313 47,034 57,347Real estate - mortgage:              1-4 family residential 1,269 759 — 12,822 14,850 573,700 588,550Commercial 220 153 — 27,425 27,798 243,108 270,906Consumer 97 13 — 104 214 43,332 43,546Total $1,685 $925 $76 $51,131 $53,817 $964,732 $1,018,549PI loans              Commercial and agricultural $77 $— $2,235 $— $2,312 $9,106 $11,418Real estate - construction — — 2,884 — 2,884 7,312 10,196Real estate - mortgage:             1-4 family residential 10 — 5,242 — 5,252 24,460 29,712Commercial 174 594 19,228 — 19,996 104,182 124,178Consumer 7 — 15 — 22 1,067 1,089Total $268 $594 $29,604 $— $30,466 $146,127 $176,593Total Loans $1,953 $1,519 $29,680 $51,131 $84,283 $1,110,859 $1,195,142The following table presents an aging analysis of accruing and nonaccruing loans as of December 31, 2012:(dollars in thousands) Accruing          30-59 days past due 60-89 days past due More than 90 days past due Nonaccrual Total past due and nonaccrual Current and accruing Total LoansPC and Originated Loans              Commercial and agricultural $515 $— $50 $2,746 $3,311 $61,727 $65,038Real estate - construction 26 119 — 14,297 14,442 41,290 55,732Real estate - mortgage:              1-4 family residential 6,173 880 — 18,372 25,425 488,898 514,323Commercial 617 — 177 43,621 44,415 226,948 271,363Consumer 24 — — 206 230 41,957 42,187Total $7,355 $999 $227 $79,242 $87,823 $860,820 $948,643PI loans              Commercial and agricultural $100 $1 $1,103 $— $1,204 $13,462 $14,666Real estate - construction 117 — 655 — 772 1,910 2,682Real estate - mortgage:              1-4 family residential 1,308 495 4,678 — 6,481 32,734 39,215Commercial 2,559 4,300 17,384 — 24,243 146,230 170,473Consumer 4 — 13 — 17 1,339 1,356Total $4,088 $4,796 $23,833 $— $32,717 $195,675 $228,392Total Loans $11,443 $5,795 $24,060 $79,242 $120,540 $1,056,495 $1,177,035All PI loans are considered to be accruing for all periods presented, in accordance with ASC 310-30.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Schedule of Impaired Loans Receivables                          | The following table summarizes information relative to impaired loans for the dates indicated:  September 30, 2013 December 31, 2012(dollars in thousands) Balance Associated Reserves Balance Associated ReservesImpaired loans, not individually reviewed for impairment $4,550 $— $6,017 $—Impaired loans, individually reviewed, with no impairment 49,356 — 62,282 —Impaired loans, individually reviewed, with impairment 2,963 486 15,312 1,737Total impaired loans, excluding purchased impaired * $56,869 $486 $83,611 $1,737         Purchased impaired loans with subsequent deterioration $147,852 4,066 $192,115 5,373Purchased impaired loans with no subsequent deterioration $28,741 — $36,277 —Total Reserves   $4,552   $7,110         Average impaired loans calculated using a simple average $61,837   $94,754  * Included at September 30, 2013 and December 31, 2012 were $6.7 million and $4.5 million, respectively, in restructured and performing loans.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Schedule of Loans, Non Accrual Status                           | The following table presents loans held for investment on nonaccrual status by loan class for the dates indicated:(dollars in thousands)      September 30, 2013 December 31, 2012Loans held for investment:    Commercial and agricultural $590 $2,746Real estate - construction 10,190 14,297Real estate - mortgage:    1-4 family residential 12,822 18,372Commercial 27,425 43,621Consumer 104 206Total nonaccrual loans $51,131 $79,242Loans more than 90 days delinquent, still on accrual 76 227Total nonperforming loans $51,207 $79,469                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Impaired Loans                                                  | The following table presents individually reviewed impaired loans and purchased impaired loans with subsequent credit deterioration, segregated by portfolio segment, and the corresponding reserve for impaired loan losses as of September 30, 2013:    Unpaid  (dollars in thousands) Recorded Principal Related  Investment Balance AllowanceWith no related allowance recorded:        Commercial and agricultural $416 $776 $—  Real estate - construction 9,900 14,246 —  Real estate - mortgage:      1-4 family residential 10,465 13,416 —Commercial 28,576 34,748 —  Consumer — — —Total $49,357 $63,186 $—With an allowance recorded:        Commercial and agricultural $— $— $—  Real estate - construction 97 112 1  Real estate - mortgage:      1-4 family residential 2,595 2,994 446Commercial 271 397 39  Consumer — — —Total $2,963 $3,503 $486Total individually evaluated impaired loans        Commercial and agricultural $416 $776 $—  Real estate - construction 9,997 14,358 1  Real estate - mortgage:      1-4 family residential 13,060 16,410 446Commercial 28,847 35,145 39  Consumer — — —Total $52,320 $66,689 $486       PI loans with subsequent credit deterioration:        Commercial and agricultural $8,821 $9,042 $34  Real estate - construction 8,258 8,897 747  Real estate - mortgage:           1-4 family residential 26,661 27,130 527     Commercial 103,028 106,249 2,567  Consumer 1,084 848 191Total $147,852 $152,166 $4,066The following table presents individually reviewed impaired loans, and purchased impaired loans with subsequent credit deterioration, segregated by portfolio segment, and the corresponding reserve for impaired loan losses as of December 31, 2012:    Unpaid  (dollars in thousands) Recorded Principal Related  Investment Balance AllowanceWith no related allowance recorded:        Commercial and agricultural $1,755 $2,608 $—  Real estate - construction 11,875 18,553 —  Real estate - mortgage:      1-4 family residential 16,437 20,764 —Commercial 32,215 38,585 —  Consumer — — —Total $62,282 $80,510 $—With an allowance recorded:        Commercial and agricultural $579 $602 $282  Real estate - construction 1,658 1,843 82  Real estate - mortgage:      1-4 family residential 1,681 1,745 607Commercial 11,394 14,714 766  Consumer — — —Total $15,312 $18,904 $1,737Total individually evaluated impaired loans        Commercial and agricultural $2,334 $3,210 $282  Real estate - construction 13,533 20,396 82  Real estate - mortgage:      1-4 family residential 18,118 22,509 607Commercial 43,609 53,299 766  Consumer — — —Total $77,594 $99,414 $1,737PI loans with subsequent credit deterioration:        Commercial and agricultural $11,533 $11,728 $524  Real estate - construction 2,285 2,236 200  Real estate - mortgage:           1-4 family residential 34,961 35,802 711     Commercial 141,974 145,704 3,388  Consumer 1,362 1,147 550Total $192,115 $196,617 $5,373 |
| Impaired Loans, Average Recorded Investment and Interest Income | The following summary includes impaired loans individually reviewed as well as impaired loans held for sale.  Average recorded investment and interest income recognized on impaired loans, segregated by portfolio segment, is shown in the following tables as of September 30, 2013 and September 30, 2012:  For Three Months Ended For Three Months Ended  September 30, 2013 September 30, 2012  Average Interest Average Interest(dollars in thousands) Recorded Income Recorded Income  Investment Recognized Investment RecognizedWith no related allowance recorded:          Commercial and agricultural $434 $— $1,557 $56  Real estate - construction 10,006 3 15,484 104  Real estate - mortgage:        1-4 family residential 10,516 — 14,265 81Commercial 27,844 4 44,480 567  Consumer — — 162 4Total $48,800 $7 $75,948 $812With an allowance recorded:          Commercial and agricultural $— $— $1,274 $6  Real estate - construction 97 — 2,802 9  Real estate - mortgage:        1-4 family residential 2,605 — 6,436 41Commercial 273 — 4,689 27  Consumer — — 100 1Total $2,975 $— $15,301 $84Total:          Commercial and agricultural $434 $— $2,831 $62  Real estate - construction 10,103 3 18,286 113  Real estate - mortgage:        1-4 family residential 13,121 — 20,701 122Commercial 28,117 4 49,169 594  Consumer — — 262 5Total $51,775 $7 $91,249 $896  For Nine Months Ended For Nine Months Ended  September 30, 2013 September 30, 2012  Average Interest Average Interest(dollars in thousands) Recorded Income Recorded Income  Investment Recognized Investment RecognizedWith no related allowance recorded:          Commercial and agricultural $455 $7 $1,879 $152  Real estate - construction 10,300 23 18,140 350  Real estate - mortgage:        1-4 family residential 10,442 14 15,096 292Commercial 29,288 58 46,051 1,388  Consumer — — 279 6Total $50,485 $102 $81,445 $2,188With an allowance recorded:          Commercial and agricultural $107 $— $1,266 $36  Real estate - construction 220 6 2,873 32  Real estate - mortgage:        1-4 family residential 1,682 4 6,869 163Commercial 3,933 — 4,687 145  Consumer 167 1 95 2Total $6,109 $11 $15,790 $378Total:          Commercial and agricultural $562 $7 $3,145 $188  Real estate - construction 10,520 29 21,013 382  Real estate - mortgage:        1-4 family residential 12,124 18 21,965 455Commercial 33,221 58 50,738 1,533  Consumer 167 1 374 8Total $56,594 $113 $97,235 $2,566                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Schedule of Loans Receivable, Sold Loans                        | The following table presents sold loans by portfolio segment for the periods indicated below: For Three Months Ended For Three Months Ended September 30, 2013 September 30, 2012(dollars in thousands)Number Recorded Contract Number Recorded Contract of Loans Investment Pricing of Loans Investment PricingCommercial and agricultural— $— $— — $— $—Real estate - construction— — — — — —Real estate - mortgage:           1-4 family residential— — — 1 602 540Commercial— — — — — —Consumer— — — — — —Total— $— $— 1$602$540 For Nine Months Ended For Nine Months Ended September 30, 2013 September 30, 2012(dollars in thousands)Number Recorded Contract Number Recorded Contract of Loans Investment Pricing of Loans Investment PricingCommercial and agricultural— $— $— — $— $—Real estate - construction— — — — — —Real estate - mortgage:           1-4 family residential— — — 7 1,865 1,896Commercial— — — 2 4,402 4,590Consumer— — — — — —Total— $— $— 9$6,267 $6,486                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Schedule of Loans Recievable, Acquired Loans                    | The following table presents the balance of all Granite Purchased Loans:  At September 30, 2013(dollars in thousands) Purchased Impaired Purchased Contractual Total Purchased Loans UnpaidPrincipalBalanceCommercial and agricultural $11,418 $4,874 $16,292 $15,597Real estate - construction 10,196 — 10,196 9,902Real estate - mortgage:           1-4 family residential 29,712 22,833 52,545 53,476   Commercial 124,178 381 124,559 125,395Consumer 1,089 — 1,089 860       Total $176,593 $28,088 $204,681 $205,230  At December 31, 2012(dollars in thousands) Purchased Impaired Purchased Contractual TotalPurchased Loans UnpaidPrincipalBalanceCommercial and agricultural $14,666 $7,311 $21,977 $21,692Real estate - construction 2,682 — 2,682 2,677Real estate - mortgage:           1-4 family residential 39,215 27,484 66,699 69,200   Commercial 170,467 49 170,516 176,347Consumer 1,362 — 1,362 1,144       Total $228,392 $34,844 $263,236 $271,060                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Deteriorated Loans Acquired, Accretable Yield Movement Schedule | The tables below include only those Granite Purchased Loans accounted for under the expected cash flow method (PI loans) for the periods indicated.  These tables do not include PC loans, including Granite Purchased PC loans or purchased performing residential mortgage loans.   For Three Months Ended For Three Months Ended  September 30, 2013 September 30, 2012  Purchased Impaired Purchased Impaired(dollars in thousands) Carrying Amount FutureAccretion Carrying Amount Future AccretionBalance, beginning of period $189,159 $28,706 $287,092 $41,133  Accretion 4,283 (4,283) 4,568 (4,568)  Increase in future accretion — — — —  Payments received (16,225) — (34,043) —  Foreclosed and transferred to OREO (624) — (5,412) —Subtotal before allowance 176,593 24,423 252,205 36,565Allowance for credit losses (4,066) — (3,296) —Net carrying amount, end of period $172,527 $24,423 $248,909 $36,565                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Allowance for Loan Losses                                       | An analysis of the changes in the ALL is as follows:  For Three Months Ended For Nine Months Ended(dollars in thousands) September 30, 2013 September 30, 2012 September 30, 2013 September 30, 2012Balance, beginning of period $25,085 $38,551 $29,314 $39,360Provision for (recoveries of) losses charged to continuing operations (350) 32 (1,297) 10,877Net charge-offs:        Charge-offs (1,724) (9,276) (10,836) (23,580)Recoveries 2,376 1,552 8,206 4,202Net recoveries (charge-offs) 652 (7,724) (2,630) (19,378)Balance, end of period $25,387 $30,859 $25,387 $30,859Annualized net charge-offs (recoveries) during the period to average loans (0.22)% 2.46% 0.31% 2.06%Annualized net charge-offs (recoveries) during the period to ALL (10.19)% 100.12% 13.85% 83.73%Allowance for loan losses to loans held for investment (1) 2.12 % 2.51% 2.12% 2.51%(1) Excludes discontinued operations.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Allowance for Loan Losses by Portfolio Segment                  | The following table presents ALL activity by portfolio segment for the three months ended September 30, 2013:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer Total            ALL:            Beginning balance at July 1, 2013 $2,192 $5,652 $7,400 $7,387 $2,454 $25,085Charge-offs (2) (36) (394) (592) (700) (1,724)Recoveries 465 1,039 285 357 230 2,376Provision (45) (1,560) 1,493 (677) 439 (350)Ending balance at September 30, 2013 $2,610 $5,095 $8,784 $6,475 $2,423 $25,387The following table presents ALL activity by portfolio segment for the three months ended September 30, 2012:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:                        Beginning balance at July 1, 2012 $7,151 $11,320 $8,784 $9,218 $2,078 $38,551Charge-offs (1,156) (2,465) (1,646) (2,602) (1,407) (9,276)Recoveries 286 323 69 388 486 1,552Provision (1,128) (3,195) 2,787 54 1,514 32Ending balance at September 30, 2012 $5,153 $5,983 $9,994 $7,058 $2,671 $30,859The following table presents ALL activity by portfolio segment for the nine months ended September 30, 2013:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer Total             ALL:            Beginning balance at January 1, 2013 $3,238 $4,987 $8,701 $9,627 $2,761 $29,314Charge-offs (1,196) (964) (3,563) (2,853) (2,260) (10,836)Recoveries 1,376 2,106 962 2,363 1,399 8,206Provision (808) (1,034) 2,684 (2,662) 523 (1,297)Ending balance at September 30, 2013 $2,610 $5,095 $8,784 $6,475 $2,423 $25,387The following table presents ALL activity by portfolio segment for the nine months ended September 30, 2012:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:            Beginning balance at January 1, 2012 $5,776 $11,995 $8,885 $11,063 $1,641 $39,360Charge-offs (2,774) (8,761) (4,805) (3,594) (3,646) (23,580)Recoveries 777 1,169 447 725 1,084 4,202Provision 1,374 1,580 5,467 (1,136) 3,592 10,877Ending balance at September 30, 2012 $5,153 $5,983 $9,994 $7,058 $2,671 $30,859                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Allowance for Loan Losses, Impairment Methodology               | The following table details the recorded investment in loans related to each segment in the allowance for loan losses by portfolio segment and disaggregated on the basis of impairment evaluation methodology at September 30, 2013:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:              Individually evaluated for impairment $— $1 $446 $39 $— $486  Collectively evaluated for impairment 2,576 4,347 7,811 3,869 2,232 20,835  PI loans evaluated for credit impairment 34 747 527 2,567 191 4,066  PI loans with no credit deterioration — — — — — —Total ALL $2,610 $5,095 $8,784 $6,475 $2,423 $25,387Loans held for investment              Individually evaluated for impairment $416 $9,998 $13,060 $28,846 $— $52,320  Collectively evaluated for impairment 57,783 47,348 575,490 242,062 43,546 966,229  PI loans with subsequent credit deterioration 8,821 8,258 26,661 103,028 1,084 147,852  PI loans with no credit deterioration 2,597 1,938 3,051 21,150 5 28,741Total loans $69,617 $67,542 $618,262 $395,086 $44,635 $1,195,142The following table details the recorded investment in loans related to each segment in the allowance for loan losses by portfolio segment and disaggregated on the basis of impairment evaluation methodology at December 31, 2012:       Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:              Individually evaluated for impairment $282 $82 $607 $766 $— $1,737  Collectively evaluated for impairment 2,432 4,705 7,383 5,473 2,211 22,204  PI loans evaluated for credit impairment 524 200 711 3,388 550 5,373  PI loans with no credit deterioration — — — — — —Total ALL $3,238 $4,987 $8,701 $9,627 $2,761 $29,314Loans held for investment              Individually evaluated for impairment $2,334 $13,533 $18,118 $43,609 $— $77,594  Collectively evaluated for impairment 62,704 42,199 496,205 227,760 42,181 871,049  PI loans with subsequent credit deterioration 11,533 2,285 34,961 141,974 1,362 192,115  PI loans with no credit deterioration 3,133 397 4,254 28,493 — 36,277Total loans $79,704 $58,414 $553,538 $441,836 $43,543 $1,177,035                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Troubled Debt Restructurings on Loans                           | The following tables presents a breakdown of troubled debt restructurings that were restructured during the three months and nine months ended September 30, 2013 and September 30, 2012, segregated by portfolio segment:  Three Months Ended September 30, 2013 For Three Months Ended September 30, 2012    Pre-Modification Post-Modification   Pre-Modification Post-Modification    Outstanding Outstanding   Outstanding Outstanding(dollars in thousands) Number Recorded Recorded Number Recorded Recorded  of Loans Investment Investment of Loans Investment InvestmentCommercial and agricultural — $— $— — $— $—Real estate - construction — — — — — —Real estate - mortgage:               1-4 family residential — — — 1 202 202   Commercial — — — — — —Consumer — — — — — —    Total — $— $— 1 $202 $202  For Nine Months Ended September 30, 2013 For Nine Months Ended September 30, 2012    Pre-Modification Post-Modification   Pre-Modification Post-Modification    Outstanding Outstanding   Outstanding Outstanding(dollars in thousands) Number Recorded Recorded Number Recorded Recorded  of Loans Investment Investment of Loans Investment InvestmentCommercial and agricultural — $— $— — $— $—Real estate - construction — — — 9 2,526 1,603Real estate - mortgage:               1-4 family residential 9 2,733 2,630 3 260 260   Commercial 2 1,611 1,195 8 1,356 1,353Consumer — — — — — —    Total 11 $4,344 $3,825 20 $4,142 $3,216                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of financing receivables (examples of financing receivables include loans, trade accounts receivable and notes receivable) and activity in the allowance for credit losses account presented by porfolio segment.
+ References
No definition available.
+ Details**Name:**cob_AllowanceForCreditLossesOnFinancingReceivablesByPortfolioSegmentTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of financing receivables presetned based on the basis of impairment methodology.
+ References
No definition available.
+ Details**Name:**cob_AllowanceForCreditLossesOnFinancingReceivablesImpairmentMethodologyTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Rollforward of accretable yield movement for certain loans acquired in trasfer not accounted for as debt securities.
+ References
No definition available.
+ Details**Name:**cob_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldMovementScheduleTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabluar disclosure of recorded average investment and interest income of impaired financing receivables.
+ References
No definition available.
+ Details**Name:**cob_ImpairedFinancingReceivablesAverageRecordedInvestmentAndInterestIncomeTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of impaired loans receivable.
+ References
No definition available.
+ Details**Name:**cob_ScheduleOfImpairedLoansReceivableTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of loans sold to third parties without recourse.  Includes number of loans sold, recorded investment amount and contract pricing.
+ References
No definition available.
+ Details**Name:**cob_ScheduleOfLoansReceivableSalesTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of acquired loans. Includes both impaired and nonimpaired balances.
+ References
No definition available.
+ Details**Name:**cob_ScheduleOfLoansRecievableAcquiredLoansTableTextBlock**Namespace Prefix:**cob_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of financing receivables (examples of financing receivables include loans, trade accounts receivable and notes receivable) and activity in the allowance for credit losses account.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524
+ Details**Name:**us-gaap_AllowanceForCreditLossesOnFinancingReceivablesTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of financing receivables by credit quality indicator. The credit quality indicator is a statistic about the credit quality of financing receivables. Examples include, but not limited to, consumer credit risk scores, credit-rating-agency ratings, an entity's internal credit risk grades, loan-to-value ratios, collateral, collection experience and other internal metrics.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 29 -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953659-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 55 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7880640&loc=SL6953803-111525
+ Details**Name:**us-gaap_FinancingReceivableCreditQualityIndicatorsTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of impaired financing receivables.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivablesTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_LoansReceivableNetAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of financing receivables that are past due but not impaired, financing receivables that are 90 days past due and still accruing, and financing receivables on nonaccrual status.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5111-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953401-111524
+ Details**Name:**us-gaap_PastDueFinancingReceivablesTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of nonaccrual and past due financing receivables (such as loans and trade receivables), including: (a) the recorded investment in loans and trade receivables, if applicable, on nonaccrual status as of each balance sheet date (b) the recorded investment in loans and trade receivables, if applicable, past due 90 days or more and still accruing.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5111-111524
+ Details**Name:**us-gaap_ScheduleOfFinancingReceivablesNonAccrualStatusTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of financing receivables and troubled debt restructurings.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953682-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953676-111524
+ Details**Name:**us-gaap_TroubledDebtRestructuringsOnFinancingReceivablesTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |