| **Loans and Allowance for Loan Losses (Tables)**                | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **Loans Receivable, Net [Abstract]**                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Past Due Loans                                                  | The following table presents an aging analysis of accruing and nonaccruing loans as of June 30, 2014:(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 $— $— $— $400 $400 $76,908 $77,308Real estate - construction 136 — — 2,773 2,909 58,678 61,587Real estate - mortgage:              1-4 family residential 384 1,007 76 9,007 10,474 630,002 640,476Commercial 84 133 206 19,192 19,615 273,039 292,654Consumer 79 7 — 31 117 55,799 55,916Total $683 $1,147 $282 $31,403 $33,515 $1,094,426 $1,127,941PI loans              Commercial and agricultural $69 $11 $2,250 $— $2,330 $6,694 $9,024Real estate - construction — — 4,203 — 4,203 6,234 10,437Real estate - mortgage:             1-4 family residential 289 58 2,921 — 3,268 16,260 19,528Commercial 26 254 13,252 — 13,532 88,315 101,847Consumer 6 2 13 — 21 1,067 1,088Total $390 $325 $22,639 $— $23,354 $118,570 $141,924Total Loans $1,073 $1,472 $22,921 $31,403 $56,869 $1,212,996 $1,269,865The following table presents an aging analysis of accruing and nonaccruing loans as of December 31, 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 $18 $43 $— $516 $577 $60,946 $61,523Real estate - construction 168 634 — 4,677 5,479 48,711 54,190Real estate - mortgage:              1-4 family residential 3,454 522 — 11,580 15,556 593,698 609,254Commercial 1,765 77 — 18,380 20,222 261,524 281,746Consumer 56 17 — 12 85 43,798 43,883Total $5,461 $1,293 $— $35,165 $41,919 $1,008,677 $1,050,596PI loans              Commercial and agricultural $35 $16 $1,977 $— $2,028 $8,701 $10,729Real estate - construction 48 — 2,758 — 2,806 7,087 9,893Real estate - mortgage:              1-4 family residential 135 9 2,907 — 3,051 23,802 26,853Commercial 903 — 17,479 — 18,382 94,796 113,178Consumer 6 — 12 — 18 981 999Total $1,127 $25 $25,133 $— $26,285 $135,367 $161,652Total Loans $6,588 $1,318 $25,133 $35,165 $68,204 $1,144,044 $1,212,248                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Loan Credit Quality Indicators                                  | The following table presents loans held for investment balances by risk grade as of June 30, 2014:(dollars in thousands) Pass Special Mention Substandard Doubtful    (Ratings 1-5) (Rating 6) (Rating 7) (Rating 8) TotalCommercial and agricultural $81,579 $1,361 $3,392 $— $86,332Real estate - construction 61,125 2,930 7,969 — 72,024Real estate - mortgage:          1-4 family residential 633,335 8,347 18,322 — 660,004Commercial 316,326 28,451 49,724 — 394,501Consumer 56,614 19 63 308 57,004Total $1,148,979 $41,108 $79,470 $308 $1,269,865The following table presents loans held for investment balances by risk grade as of December 31, 2013:(dollars in thousands) Pass Special Mention Substandard Doubtful    (Ratings 1-5) (Rating 6) (Rating 7) (Rating 8) TotalCommercial and agricultural $67,277 $1,262 $3,713 $— $72,252Real estate - construction 50,138 3,984 9,961 — 64,083Real estate - mortgage:          1-4 family residential 601,304 10,887 23,916 — 636,107Commercial 307,661 29,711 57,552 — 394,924Consumer 44,450 40 47 345 44,882Total $1,070,830 $45,884 $95,189 $345 $1,212,248                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Schedule of Impaired Loans Receivables                          | The following table summarizes information relative to impaired loans for the dates indicated:  June 30, 2014 December 31, 2013(dollars in thousands) Recorded Investment Associated Reserves Recorded Investment Associated ReservesImpaired loans, not individually reviewed for impairment $4,750 $— $4,612 $—Impaired loans, individually reviewed, with no impairment 29,890 — 39,865 —Impaired loans, individually reviewed, with impairment 9,693 855 2,965 927Total impaired loans, excluding purchased impaired * $44,333 $855 $47,442 $927         Purchased impaired loans with subsequent deterioration $141,924 4,123 $161,307 5,560Purchased impaired loans with no subsequent deterioration $— — $345 —Total Reserves   $4,978   $6,487         Average impaired loans calculated using a simple average $45,888   $65,527  * Included at June 30, 2014 and December 31, 2013 were $12.9 million and $12.1 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)      June 30, 2014 December 31, 2013Loans held for investment:    Commercial and agricultural $400 $516Real estate - construction 2,773 4,677Real estate - mortgage:    1-4 family residential 9,007 11,580Commercial 19,192 18,380Consumer 31 12Total nonaccrual loans $31,403 $35,165Loans more than 90 days delinquent, still on accrual 282 —Total nonperforming loans $31,685 $35,165                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| 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, 2014:    Unpaid  (dollars in thousands) Recorded Principal Related  Investment Balance AllowanceWith no related allowance recorded:        Commercial and agricultural $242 $485 $—  Real estate - construction 2,179 2,736 —  Real estate - mortgage:      1-4 family residential 8,220 10,940 —Commercial 19,249 24,655 —  Consumer — — —Total $29,890 $38,816 $—With an allowance recorded:        Commercial and agricultural $— $— $—  Real estate - construction 547 643 280  Real estate - mortgage:      1-4 family residential 3,698 4,020 452Commercial 5,448 5,792 123  Consumer — — —Total $9,693 $10,455 $855Total individually evaluated impaired loans        Commercial and agricultural $242 $485 $—  Real estate - construction 2,726 3,379 280  Real estate - mortgage:      1-4 family residential 11,918 14,960 452Commercial 24,697 30,447 123  Consumer — — —Total $39,583 $49,271 $855       PI loans with subsequent credit deterioration:        Commercial and agricultural $9,024 $7,823 $581  Real estate - construction 10,437 11,521 729  Real estate - mortgage:           1-4 family residential 19,528 21,076 411     Commercial 101,847 109,289 2,212  Consumer 1,088 712 190Total $141,924 $150,421 $4,123The 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, 2013:    Unpaid  (dollars in thousands) Recorded Principal Related  Investment Balance AllowanceWith no related allowance recorded:        Commercial and agricultural $398 $643 $—  Real estate - construction 4,734 8,893 —  Real estate - mortgage:      1-4 family residential 11,154 14,431 —Commercial 23,579 28,905 —  Consumer — — —Total $39,865 $52,872 $—With an allowance recorded:        Commercial and agricultural $— $— $—  Real estate - construction — — —  Real estate - mortgage:      1-4 family residential 2,965 3,032 927Commercial — — —  Consumer — — —Total $2,965 $3,032 $927Total individually evaluated impaired loans        Commercial and agricultural $398 $643 $—  Real estate - construction 4,734 8,893 —  Real estate - mortgage:      1-4 family residential 14,119 17,463 927Commercial 23,579 28,905 —  Consumer — — —Total $42,830 $55,904 $927PI loans with subsequent credit deterioration:        Commercial and agricultural $10,729 $10,344 $382  Real estate - construction 9,792 11,216 1,015  Real estate - mortgage:           1-4 family residential 26,628 28,143 724     Commercial 113,178 121,813 3,251  Consumer 980 785 188Total $161,307 $172,301 $5,560 |
| Impaired Loans, Average Recorded Investment and Interest Income | The following summary includes impaired loans individually reviewed.  Average recorded investment and interest income recognized on impaired loans, segregated by portfolio segment, is shown in the following tables as of June 30, 2014 and June 30, 2013:  For Three Months Ended For Three Months Ended  June 30, 2014 June 30, 2013  Average Interest Average Interest(dollars in thousands) Recorded Income Recorded Income  Investment Recognized Investment RecognizedWith no related allowance recorded:          Commercial and agricultural $242 $— $1,398 $1  Real estate - construction 2,191 7 9,513 —  Real estate - mortgage:        1-4 family residential 8,263 23 12,662 9Commercial 19,686 33 30,466 25  Consumer — — — —Total $30,382 $63 $54,039 $35With an allowance recorded:          Commercial and agricultural $— $— $107 $—  Real estate - construction 583 — 219 3  Real estate - mortgage:        1-4 family residential 3,706 14 1,662 1Commercial 5,474 33 3,912 —  Consumer — — 164 —Total $9,763 $47 $6,064 $4Total:          Commercial and agricultural $242 $— $1,505 $1  Real estate - construction 2,774 7 9,732 3  Real estate - mortgage:        1-4 family residential 11,969 37 14,324 10Commercial 25,160 66 34,378 25  Consumer — — 164 —Total $40,145 $110 $60,103 $39  For Six Months Ended For Six Months Ended  June 30, 2014 June 30, 2013  Average Interest Average Interest(dollars in thousands) Recorded Income Recorded Income  Investment Recognized Investment RecognizedWith no related allowance recorded:          Commercial and agricultural $242 $— $1,414 $8  Real estate - construction 2,209 18 9,705 —  Real estate - mortgage:        1-4 family residential 8,250 51 12,643 33Commercial 20,004 137 31,042 144  Consumer — — — —Total $30,705 $206 $54,804 $185With an allowance recorded:          Commercial and agricultural $— $— $107 $—  Real estate - construction 594 — 220 6  Real estate - mortgage:        1-4 family residential 3,722 32 1,682 4Commercial 5,504 91 3,933 —  Consumer — — 167 1Total $9,820 $123 $6,109 $11Total:          Commercial and agricultural $242 $— $1,521 $8  Real estate - construction 2,803 18 9,925 6  Real estate - mortgage:        1-4 family residential 11,972 83 14,325 37Commercial 25,508 228 34,975 144  Consumer — — 167 1Total $40,525 $329 $60,913 $196                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Schedule of Loans Receivable, Acquired Loans                    | The following table presents the balance of all Granite Purchased Loans:  At June 30, 2014(dollars in thousands) Purchased Impaired Purchased Contractual Total Purchased Loans UnpaidPrincipalBalanceCommercial and agricultural $9,024 $3,727 $12,751 $11,627Real estate - construction 10,437 — 10,437 11,521Real estate - mortgage:           1-4 family residential 19,528 24,232 43,760 46,072   Commercial 101,847 11 101,858 109,300Consumer 1,088 — 1,088 712       Total $141,924 $27,970 $169,894 $179,232  At December 31, 2013(dollars in thousands) Purchased Impaired Purchased Contractual TotalPurchased Loans UnpaidPrincipalBalanceCommercial and agricultural $10,729 $5,948 $16,677 $16,452Real estate - construction 9,893 — 9,893 11,368Real estate - mortgage:           1-4 family residential 26,853 22,127 48,980 51,359   Commercial 113,178 373 113,551 122,197Consumer 999 — 999 798       Total $161,652 $28,448 $190,100 $202,174                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 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, 2014 June 30, 2013  Purchased Impaired Purchased Impaired(dollars in thousands) Carrying Amount FutureAccretion Carrying Amount Future AccretionBalance, beginning of period $149,033 $28,327 $205,884 $26,096  Accretion 2,415 (2,415) 4,191 (4,191)  Increase in future accretion — 1,852 — 6,801  Payments received (9,524) — (20,403) —  Foreclosed and transferred to OREO — — (513) —Subtotal before allowance 141,924 27,764 189,159 28,706Allowance for credit losses (4,123) — (4,066) —Net carrying amount, end of period $137,801 $27,764 $185,093 $28,706  For Six Months Ended For Six Months Ended  June 30, 2014 June 30, 2013  Purchased Impaired Purchased Impaired(dollars in thousands) Carrying Amount FutureAccretion Carrying Amount Future AccretionBalance, beginning of period $161,652 $29,987 $228,392 $30,299  Accretion 5,079 (5,079) 8,394 (8,394)Increase in future accretion — 2,856 — 6,801  Reclassification of loans and adjustments (4,180) — — —  Payments received (20,605) — (46,331) —  Foreclosed and transferred to OREO (22) — (1,296) —Subtotal before allowance 141,924 27,764 189,159 28,706Allowance for credit losses (4,123) — (4,066) —Net carrying amount, end of period $137,801 $27,764 $185,093 $28,706                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| 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, 2014 June 30, 2013 June 30, 2014 June 30, 2013Balance, beginning of period $26,039 $29,641 $26,785 $29,314Recovery of losses charged to continuing operations (1,685) (1,057) (2,369) (947)Net recoveries (charge-offs):        Charge-offs (2,033) (6,102) (4,010) (9,113)Recoveries 1,654 2,603 3,569 5,831Net charge-offs (379) (3,499) (441) (3,282)Balance, end of period $23,975 $25,085 $23,975 $25,085Annualized net charge-offs during the period to average loans held for investment 0.12% 1.26% 0.07% 0.59%Annualized net charge-offs during the period to ALL 6.34% 55.79% 3.71% 26.17%Allowance for loan losses to loans held for investment 1.89% 2.11% 1.89% 2.11%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Allowance for Loan Losses by Portfolio Segment                  | The following table presents ALL activity by portfolio segment for the three months ended June 30, 2014:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer Total            ALL:            Beginning balance April 1, 2014 $3,441 $5,308 $7,923 $6,966 $2,401 $26,039Charge-offs (621) (91) (151) (730) (440) (2,033)Recoveries 262 363 263 527 239 1,654Provision (recovery of provision) 426 (802) (625) (1,097) 413 (1,685)Ending balance June 30, 2014 $3,508 $4,778 $7,410 $5,666 $2,613 $23,975The 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 TotalALL:                        Beginning balance 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 (recovery of provision) (939) 371 642 (1,608) 477 (1,057)Ending balance 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, 2014:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:            Beginning balance at January 1, 2014 $2,931 $5,233 $8,869 $7,195 $2,557 $26,785Charge-offs (1,010) (624) (635) (796) (945) (4,010)Recoveries 654 1,327 498 593 497 3,569Provision (recovery of provision) 933 (1,158) (1,322) (1,326) 504 (2,369)Ending balance at June 30, 2014 $3,508 $4,778 $7,410 $5,666 $2,613 $23,975The 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 TotalALL:            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 (recovery of provision) (763) 526 1,191 (1,985) 84 (947)Ending balance at June 30, 2013 $2,192 $5,652 $7,400 $7,387 $2,454 $25,085                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| 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, 2014:      Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:              Individually evaluated for impairment $— $280 $452 $123 $— $855  Collectively evaluated for impairment 2,927 3,769 6,547 3,331 2,423 18,997  PI loans evaluated for credit impairment 581 729 411 2,212 190 4,123Total ALL $3,508 $4,778 $7,410 $5,666 $2,613 $23,975Loans held for investment              Individually evaluated for impairment $242 $2,726 $11,929 $24,698 $— $39,595  Collectively evaluated for impairment 77,066 58,861 628,547 267,956 55,916 1,088,346  PI loans with subsequent credit deterioration 9,024 10,437 19,528 101,847 1,088 141,924Total loans $86,332 $72,024 $660,004 $394,501 $57,004 $1,269,865The 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, 2013:       Real Estate - Mortgage    (dollars in thousands) Commercial and Agricultural Real Estate - Construction 1-4 Family Residential Commercial Consumer TotalALL:              Individually evaluated for impairment $— $— $927 $— $— $927  Collectively evaluated for impairment 2,549 4,218 7,218 3,944 2,369 20,298  PI loans evaluated for credit impairment 382 1,015 724 3,251 188 5,560  PI loans with no credit deterioration — — — — — —Total ALL $2,931 $5,233 $8,869 $7,195 $2,557 $26,785Loans held for investment              Individually evaluated for impairment $398 $4,734 $14,119 $23,579 $— $42,830  Collectively evaluated for impairment 61,125 49,456 595,135 258,167 43,883 1,007,766  PI loans with subsequent credit deterioration 10,729 9,792 26,628 113,178 980 161,307  PI loans with no credit deterioration — 101 225 — 19 345Total loans $72,252 $64,083 $636,107 $394,924 $44,882 $1,212,248                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Troubled Debt Restructurings on Loans                           | The following tables present a breakdown of troubled debt restructurings that were restructured during the three months and six months ended June 30, 2014 and June 30, 2013, respectively, segregated by portfolio segment:  For Three Months Ended June 30, 2014 For Three Months Ended June 30, 2013    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 114Real estate - mortgage:               1-4 family residential 1 17 21 4 915 894   Commercial — — — 1 460 421Consumer — — — — — —    Total 1 $17 $21 6 $1,489 $1,429  For Six Months Ended June 30, 2014 For Six Months Ended June 30, 2013    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 114Real estate - mortgage:               1-4 family residential 7 752 828 8 2,692 2,667   Commercial — — — 2 1,611 1,228Consumer — — — — — —    Total 7 $752 $828 11 $4,417 $4,009                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

| 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 acquired loans. Includes both impaired and nonimpaired balances.
+ References
No definition available.
+ Details**Name:**cob_ScheduleofLoansReceivableAcquiredLoansTableTextBlock**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=28368275&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=28368275&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=32702940&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=28368275&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=28368275&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=28368275&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=28368275&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=28368275&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=28368275&loc=SL6953676-111524
+ Details**Name:**us-gaap_TroubledDebtRestructuringsOnFinancingReceivablesTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |