| **Loans (Tables)**                                              | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| **Loans Receivable, Net [Abstract]**                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Loan Credit Quality Indicators                                  | The following table presents loans held for investment balances by risk grade as of June 30, 2013:(dollars in thousands) Pass Special Mention Substandard Doubtful    (Ratings 1-5) (Rating 6) (Rating 7) (Rating 8) TotalCommercial and agricultural $62,760 $1,861 $4,722 $— $69,343Real estate - construction 46,440 1,891 16,305 — 64,636Real estate - mortgage:          1-4 family residential 569,013 13,692 27,932 107 610,744Commercial 300,265 29,702 70,805 — 400,772Consumer 42,971 180 493 274 43,918Total $1,021,449 $47,326 $120,257 $381 $1,189,413The 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 June 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 $433 $— $— $1,654 $2,087 $55,293 $57,380Real estate - construction 419 — — 9,783 10,202 44,171 54,373Real estate - mortgage:              1-4 family residential 1,038 19 — 15,917 16,974 560,957 577,931Commercial 410 — — 31,380 31,790 236,003 267,793Consumer 156 11 — 269 436 42,341 42,777Total $2,456 $30 $— $59,003 $61,489 $938,765 $1,000,254PI loans              Commercial and agricultural $79 $1,059 $701 $— $1,839 $10,124 $11,963Real estate - construction 189 — 2,725 — 2,914 7,349 10,263Real estate - mortgage:             1-4 family residential 73 143 3,113 — 3,329 29,484 32,813Commercial 2,019 255 15,119 — 17,393 115,586 132,979Consumer 1 — — — 1 1,140 1,141Total $2,361 $1,457 $21,658 $— $25,476 $163,683 $189,159Total Loans $4,817 $1,487 $21,658 $59,003 $86,965 $1,102,448 $1,189,413The 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:  June 30, 2013 December 31, 2012(dollars in thousands) BalanceAssociated Reserves BalanceAssociated ReservesImpaired loans, not individually reviewed for impairment $9,313$— $6,017$—Impaired loans, individually reviewed, with no impairment 51,557— 62,282—Impaired loans, individually reviewed, with impairment 5,935763 15,3121,737Total impaired loans, excluding purchased impaired * $66,805$763 $83,611$1,737       Purchased impaired loans with subsequent deterioration $161,2784,066 $192,1155,373Purchased impaired loans with no subsequent deterioration $27,881— $36,277—Total Reserves  $4,829  $7,110       Average impaired loans calculated using a simple average $72,917  $94,754                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| 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)      June 30, 2013 December 31, 2012Loans held for investment:    Commercial and agricultural $1,654 $2,746Real estate - construction 9,783 14,297Real estate - mortgage:    1-4 family residential 15,917 18,372Commercial 31,380 43,621Consumer 269 206Total nonaccrual loans $59,003 $79,242Loans more than 90 days delinquent, still on accrual — 227Total nonperforming loans $59,003 $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 June 30, 2013:    Unpaid  (dollars in thousands) Recorded Principal Related  Investment Balance AllowanceWith no related allowance recorded:        Commercial and agricultural $1,366 $1,700 $—  Real estate - construction 9,029 14,230 —  Real estate - mortgage:      1-4 family residential 12,218 17,109 —Commercial 28,944 36,430 —  Consumer — — —Total $51,557 $69,469 $—With an allowance recorded:        Commercial and agricultural $107 $316 $15  Real estate - construction 218 218 20  Real estate - mortgage:      1-4 family residential 1,615 1,704 209Commercial 3,845 5,197 369  Consumer 150 155 150Total $5,935 $7,590 $763Total individually evaluated impaired loans        Commercial and agricultural $1,473 $2,016 $15  Real estate - construction 9,247 14,448 20  Real estate - mortgage:      1-4 family residential 13,833 18,813 209Commercial 32,789 41,627 369  Consumer 150 155 150Total $57,492 $77,059 $763       PI loans with subsequent credit deterioration:        Commercial and agricultural $9,429 $9,375 $26  Real estate - construction 8,202 8,795 759  Real estate - mortgage:           1-4 family residential 29,875 30,226 504     Commercial 112,641 114,601 2,585  Consumer 1,131 907 192Total $161,278 $163,904 $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 June 30, 2013 and June 30, 2012:  For Three Months Ended For Three Months Ended  June 30, 2013 June 30, 2012  Average Interest Average Interest(dollars in thousands) Recorded Income Recorded Income  Investment Recognized Investment RecognizedWith no related allowance recorded:          Commercial and agricultural $1,398 $1 $2,170 $3  Real estate - construction 9,513 — 10,918 30  Real estate - mortgage:        1-4 family residential 12,662 9 15,944 60Commercial 30,466 25 33,630 76  Consumer — — 1,000 15Total $54,039 $35 $63,662 $184With an allowance recorded:          Commercial and agricultural $107 $— $1,790 $—  Real estate - construction 219 3 16,567 7  Real estate - mortgage:        1-4 family residential 1,662 1 8,760 76Commercial 3,912 — 15,832 151  Consumer 164 — 652 13Total $6,064 $4 $43,601 $247Total:          Commercial and agricultural $1,505 $1 $3,960 $3  Real estate - construction 9,732 3 27,485 37  Real estate - mortgage:        1-4 family residential 14,324 10 24,704 136Commercial 34,378 25 49,462 227  Consumer 164 — 1,652 28Total $60,103 $39 $107,263 $431  For Six Months Ended For Six Months Ended  June 30, 2013 June 30, 2012  Average Interest Average Interest(dollars in thousands) Recorded Income Recorded Income  Investment Recognized Investment RecognizedWith no related allowance recorded:          Commercial and agricultural $1,414 $8 $2,651 $10  Real estate - construction 9,705 — 12,166 34  Real estate - mortgage:        1-4 family residential 12,643 33 17,071 66Commercial 31,042 144 31,720 106  Consumer — — 699 15Total $54,804 $185 $64,307 $231With an allowance recorded:          Commercial and agricultural $107 $— $1,729 $—  Real estate - construction 220 6 14,308 9  Real estate - mortgage:        1-4 family residential 1,682 4 10,862 94Commercial 3,933 — 15,177 159  Consumer 167 1 432 13Total $6,109 $11 $42,508 $275Total:          Commercial and agricultural $1,521 $8 $4,380 $10  Real estate - construction 9,925 6 26,474 43  Real estate - mortgage:        1-4 family residential 14,325 37 27,933 160Commercial 34,975 144 46,897 265  Consumer 167 1 1,131 28Total $60,913 $196 $106,815 $506                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 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 June 30, 2013 June 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— — — 6 1,715 1,746Commercial— — — — — —Consumer— — — — — —Total— $— $— 6$1,715$1,746                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Schedule of Loans Recievable, Acquired Loans                    | The following table presents the balance of all Granite Purchased Loans:  At June 30, 2013(dollars in thousands) Purchased Impaired Purchased Contractual Total Purchased Loans UnpaidPrincipalBalanceCommercial and agricultural $11,964 $4,647 $16,611 $15,971Real estate - construction 10,263 — 10,263 10,095Real estate - mortgage:           1-4 family residential 32,813 24,130 56,943 58,197   Commercial 132,978 390 133,368 135,404Consumer 1,141 — 1,141 937       Total $189,159 $29,167 $218,326 $220,604  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  June 30, 2013 June 30, 2012  Purchased Impaired Purchased Impaired(dollars in thousands) Carrying Amount FutureAccretion Carrying Amount Future AccretionBalance, beginning of period $205,884 $26,096 $310,389 $42,032  Accretion 4,191 (4,191) 5,491 (5,491)  Increase in future accretion — 6,801 — 4,592  Payments received (20,403) — (27,791) —  Foreclosed and transferred to OREO (513) — (997) —Subtotal before allowance 189,159 28,706 287,092 41,133Allowance for credit losses (4,066) — (3,336) —Net carrying amount, end of period $185,093 $28,706 $283,756 $41,133                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Allowance for Loan Losses                                       | An analysis of the changes in the ALL is as follows:  For Three Months Ended For Six Months Ended(dollars in thousands) June 30, 2013 June 30, 2012 June 30, 2013 June 30, 2012Balance, beginning of period $29,641 $39,795 $29,314 $39,360Provision for losses charged to continuing operations (1,057) 7,778 (947) 10,845Net charge-offs:        Charge-offs (6,102) (10,285) (9,113) (14,300)Recoveries 2,603 1,263 5,831 2,646Net recoveries (charge-offs) (3,499) (9,022) (3,282) (11,654)Balance, end of period $25,085 $38,551 $25,085 $38,551Annualized net charge-offs (recoveries) during the period to average loans 1.26% 2.83% 0.59% 1.87%Annualized net charge-offs (recoveries) during the period to ALL 55.79% 94.13% 26.17% 60.79%Allowance for loan losses to loans held for investment (1) 2.11% 3.01% 2.11% 3.01%(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 June 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 April 1, 2013 $3,373 $5,594 $8,803 $9,291 $2,580 $29,641Charge-offs (875) (584) (2,537) (1,371) (735) (6,102)Recoveries 633 271 492 1,075 132 2,603Provision (939) 371 642 (1,608) 477 (1,057)Ending balance at June 30, 2013 $2,192 $5,652 $7,400 $7,387 $2,454 $25,085The following table presents ALL activity by portfolio segment for the three months ended June 30, 2012:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:                        Beginning balance at April 1, 2012 $6,005 $10,912 $12,103 $8,799 $1,976 $39,795Charge-offs (937) (4,521) (2,454) (954) (1,419) (10,285)Recoveries 235 244 244 262 278 1,263Provision 1,848 4,685 (1,109) 1,111 1,243 7,778Ending balance at June 30, 2012 $7,151 $11,320 $8,784 $9,218 $2,078 $38,551The following table presents ALL activity by portfolio segment for the six months ended June 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 (1,194) (928) (3,169) (2,262) (1,560) (9,113)Recoveries 911 1,067 677 2,007 1,169 5,831Provision (763) 526 1,191 (1,985) 84 (947)Ending balance at June 30, 2013 $2,192 $5,652 $7,400 $7,387 $2,454 $25,085The following table presents ALL activity by portfolio segment for the six months ended June 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 (1,631) (6,296) (3,159) (992) (2,222) (14,300)Recoveries 489 845 377 336 599 2,646Provision 2,517 4,776 2,681 (1,189) 2,060 10,845Ending balance at June 30, 2012 $7,151 $11,320 $8,784 $9,218 $2,078 $38,551                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 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 June 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 $15 $20 $209 $369 $150 $763  Collectively evaluated for impairment 2,151 4,873 6,687 4,433 2,112 20,256  PI loans evaluated for credit impairment 26 759 504 2,585 192 4,066  PI loans with no credit deterioration — — — — — —Total ALL $2,192 $5,652 $7,400 $7,387 $2,454 $25,085Loans held for investment              Individually evaluated for impairment $1,473 $9,247 $13,833 $32,789 $150 $57,492  Collectively evaluated for impairment 55,906 45,126 564,098 235,005 42,627 942,762  PI loans with subsequent credit deterioration 9,429 8,202 29,875 112,641 1,131 161,278  PI loans with no credit deterioration 2,535 2,061 2,938 20,337 10 27,881Total loans $69,343 $64,636 $610,744 $400,772 $43,918 $1,189,413The 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 six months ended June 30, 2013 and June 30, 2012, segregated by portfolio segment:  Three Months Ended June 30, 2013 For Three Months Ended June 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 1 114 114 4 369 329Real estate - mortgage:               1-4 family residential 4 915 894 — — —   Commercial 1 460 421 3 617 614Consumer — — — — — —    Total 6 $1,489 $1,429 7 $986 $943  For Six Months Ended June 30, 2013 For Six Months Ended June 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 1 114 114 9 2,526 1,603Real estate - mortgage:               1-4 family residential 8 2,692 2,667 2 58 58   Commercial 2 1,611 1,228 8 1,356 1,353Consumer — — — — — —    Total 11 $4,417 $4,009 19 $3,940 $3,014                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |

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| - 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                                                                                                                                                                                                                                                                                                                                                                        |
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| - 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                                                                                                                                                                                                                                                                                                                                                                                |
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| - 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 |
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| - 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
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
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| 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
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
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| 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
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