| **Loans and Allowance for Credit Losses (Tables)**                                            | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| **Loans and Leases Receivable Disclosure [Abstract]**                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Outstanding Balances of Loan                                                                  | The following table provides outstanding balances related to each of our loan types:  March 31, 2013 December 31, 2012 (dollars in thousands)Commercial, financial, agricultural and other$1,057,663 $1,019,822Real estate construction70,461 87,438Residential real estate1,255,515 1,241,565Commercial real estate1,243,676 1,273,661Loans to individuals591,495 582,218Total loans and leases net of unearned income$4,218,810 $4,204,704                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Credit Risk Profile by Creditworthiness                                                       | The following tables represent our credit risk profile by creditworthiness: March 31, 2013 Commercial, financial, agricultural and other Real estate construction Residential real estate Commercial real estate Loans to individuals Total (dollars in thousands)Pass$942,673 $50,664 $1,238,633 $1,140,648 $591,326 $3,963,944Non-Pass           OAEM43,909 911 5,075 59,894 2 109,791Substandard71,081 15,364 11,807 43,134 167 141,553Doubtful— 3,522 — — — 3,522Total Non-Pass114,990 19,797 16,882 103,028 169 254,866Total$1,057,663 $70,461 $1,255,515 $1,243,676 $591,495 $4,218,810  December 31, 2012 Commercial, financial, agricultural and other Real estate construction Residential real estate Commercial real estate Loans to individuals Total (dollars in thousands)Pass$925,868 $64,353 $1,224,849 $1,119,093 $582,039 $3,916,202Non-Pass           OAEM31,049 925 5,647 82,581 3 120,205Substandard62,905 18,638 11,069 71,987 176 164,775Doubtful— 3,522 — — — 3,522Total Non-Pass93,954 23,085 16,716 154,568 179 288,502Total$1,019,822 $87,438 $1,241,565 $1,273,661 $582,218 $4,204,704                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Age Analysis of Past Due Loans by Segment                                                     | The following tables delineate the aging analysis of the recorded investments in past due loans as of March 31, 2013 and December 31, 2012. Also included in these tables are loans that are 90 days or more past due and still accruing because they are well-secured and in the process of collection.  March 31, 2013 30 - 59dayspast due 60 - 89dayspastdue 90 daysandgreaterand stillaccruing Nonaccrual Total pastdue andnonaccrual Current Total (dollars in thousands)Commercial, financial, agricultural and other$3,054 $2,380 $1,108 $28,666 $35,208 $1,022,455 $1,057,663Real estate construction206 15 500 7,112 7,833 62,628 70,461Residential real estate6,282 2,420 963 9,740 19,405 1,236,110 1,255,515Commercial real estate9,903 921 279 18,456 29,559 1,214,117 1,243,676Loans to individuals2,565 576 1,077 167 4,385 587,110 591,495Total$22,010 $6,312 $3,927 $64,141 $96,390 $4,122,420 $4,218,810  December 31, 2012 30 - 59dayspast due 60 - 89dayspastdue 90 daysandgreaterand stillaccruing Nonaccrual Total pastdue andnonaccrual Current Total (dollars in thousands)Commercial, financial, agricultural and other$991 $620 $288 $29,258 $31,157 $988,665 $1,019,822Real estate construction2 19 15 9,778 9,814 77,624 87,438Residential real estate6,597 2,357 730 9,283 18,967 1,222,598 1,241,565Commercial real estate3,339 1,389 195 46,023 50,946 1,222,715 1,273,661Loans to individuals3,140 934 1,219 176 5,469 576,749 582,218Total$14,069 $5,319 $2,447 $94,518 $116,353 $4,088,351 $4,204,704                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Recorded Investment and Unpaid Principal Balance for Impaired Loans with Associated Allowance | The following tables include the recorded investment and unpaid principal balance for impaired loans with the associated allowance amount, if applicable, as of March 31, 2013 and December 31, 2012. Also presented are the average recorded investment in impaired loans and the related amount of interest recognized while the loan was considered impaired. Average balances are calculated based on month-end balances of the loans for the period reported.  March 31, 2013 December 31, 2012 Recordedinvestment Unpaidprincipalbalance Relatedallowance Recordedinvestment Unpaidprincipalbalance Relatedallowance (dollars in thousands)With no related allowance recorded:           Commercial, financial, agricultural and other$8,649 $9,601 $— $8,080 $8,983 $—Real estate construction6,122 27,005 — 8,491 35,555 —Residential real estate8,666 9,269 — 7,928 8,401 —Commercial real estate16,711 23,250 — 33,259 35,401 —Loans to individuals240 247 — 256 256 —Subtotal40,388 69,372 — 58,014 88,596 —With an allowance recorded:           Commercial, financial, agricultural and other25,702 26,655 9,846 26,532 27,412 10,331Real estate construction2,860 3,169 503 2,756 3,087 300Residential real estate2,663 2,666 1,091 2,695 2,696 780Commercial real estate6,668 7,263 1,249 17,558 17,896 6,367Loans to individuals— — — — — —Subtotal37,893 39,753 12,689 49,541 51,091 17,778Total$78,281 $109,125 $12,689 $107,555 $139,687 $17,778  For the Three-Months Ended March 31, 2013 2012 Averagerecordedinvestment InterestIncomeRecognized Averagerecordedinvestment InterestIncomeRecognized (dollars in thousands)With no related allowance recorded:       Commercial, financial, agricultural and other$8,592 $51 $3,258 $18Real estate construction7,877 — 3,646 —Residential real estate8,516 37 3,354 5Commercial real estate33,978 11 24,275 23Loans to individuals247 1 — —Subtotal59,210 100 34,533 46With an allowance recorded:       Commercial, financial, agricultural and other25,803 19 30,350 3Real estate construction2,685 13 10,432 —Residential real estate2,457 4 952 7Commercial real estate6,704 25 5,889 9Loans to individuals— — — —Subtotal37,649 61 47,623 19Total$96,859 $161 $82,156 $65         |
| Troubled Debt Restructured Loans and Commitments                                              | The following table provides detail as to the total troubled debt restructured loans and total commitments outstanding on troubled debt restructured loans: March 31, 2013 December 31, 2012 (dollars in thousands)Troubled debt restructured loans   Accrual status$14,140 $13,037Nonaccrual status32,565 50,979Total$46,705 $64,016Commitments   Letters of credit$— $1,574Unused lines of credit1,083 —Total$1,083 $1,574                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Troubled Debt Restructurings is 90 days or more past due                                      | The following tables provide detail, including specific reserve and reasons for modification, related to loans identified as troubled debt restructurings: For the Three-Months Ended March 31, 2013   Type of Modification       NumberofContracts ExtendMaturity ModifyRate ModifyPayments TotalPre-ModificationOutstandingRecordedInvestment Post-ModificationOutstandingRecordedInvestment SpecificReserve (dollars in thousands)Commercial, financial, agricultural and other2 $426 $— $12 $438 $377 $—Residential real estate9 7 214 514 735 677 —Commercial real estate1 — 244 — 244 242 —Loans to individuals4 — 23 4 27 25  Total16 $433 $481 $530 $1,444 $1,321 $— For the Three-Months Ended March 31, 2012   Type of Modification       NumberofContracts ExtendMaturity ModifyRate ModifyPayments TotalPre-ModificationOutstandingRecordedInvestment Post-ModificationOutstandingRecordedInvestment SpecificReserve (dollars in thousands)Residential real estate2 $— $97 $— $97 $53 $—                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Troubled Debt Restructuring Identified During Period                                          | The following provides information related to restructured loans that were considered to default during the three-months endedMarch 31,:  2013 2012 Number ofContracts RecordedInvestment Number ofContracts RecordedInvestment (dollars in thousands)Residential real estate1 10 — —Commercial real estate— $— 2 $980Loans to individuals1 6 — —Total2 $16 2 $980                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Allowance for Credit Losses                                                                   | The following tables provide detail related to the allowance for credit losses: For the Three-Months Ended March 31, 2013 Commercial,financial,agriculturaland other Real estateconstruction Residentialreal estate Commercialreal estate Loans toindividuals Unallocated Total (dollars in thousands)Allowance for credit losses:             Beginning Balance$19,852 $8,928 $5,908 $22,441 $4,132 $5,926 $67,187Charge-offs(538) (84) (322) (8,544) (988) — (10,476)Recoveries128 12 723 97 94 — 1,054Provision (credit)833 (1,123) (560) 4,476 901 (30) 4,497Ending Balance$20,275 $7,733 $5,749 $18,470 $4,139 $5,896 $62,262Ending balance: individually evaluated for impaired$9,846 $503 $1,091 $1,249 $— $— $12,689Ending balance: collectively evaluated for impaired10,429 7,230 4,658 17,221 4,139 5,896 49,573Loans:             Ending balance1,057,663 70,461 1,255,515 1,243,676 591,495   4,218,810Ending balance: individually evaluated for impaired33,322 8,917 7,813 21,369 —   71,421Ending balance: collectively evaluated for impaired1,024,341 61,544 1,247,702 1,222,307 591,495   4,147,389  For the Three-Months Ended March 31, 2012 Commercial,financial,agriculturaland other Real estateconstruction Residentialreal estate Commercialreal estate Loans toindividuals Unallocated Total (dollars in thousands)Allowance for credit losses:             Beginning Balance$18,200 $6,756 $8,237 $18,961 $4,244 $4,836 $61,234Charge-offs(1,914) (190) (1,712) (235) (941) — (4,992)Recoveries238 56 133 158 118 — 703Provision (credit)1,619 (195) 44 487 831 1,001 3,787Ending Balance$18,143 $6,427 $6,702 $19,371 $4,252 $5,837 $60,732Ending balance: individually evaluated for impaired$7,555 $2,891 $553 $921 $— $— $11,920Ending balance: collectively evaluated for impaired10,588 3,536 6,149 18,450 4,252 5,837 48,812Loans:             Ending balance1,051,209 64,158 1,174,572 1,264,060 574,589   4,128,588Ending balance: individually evaluated for impaired31,599 13,800 3,217 28,874 —   77,490Ending balance: collectively evaluated for impaired1,019,610 50,358 1,171,355 1,235,186 574,589   4,051,098                                                           |

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Schedule of recorded investment and unpaid principal balance for impaired loans with the associated allowance.
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Troubled debt restructurings identified during the period.
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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.
+ References
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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
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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
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| - Definition
Tabular disclosure of the various types of trade accounts and notes receivable and for each the gross carrying value, allowance, and net carrying value as of the balance sheet date. Presentation is categorized by current, noncurrent and unclassified receivables.
+ References
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| - Definition
Tabular disclosure of financing receivables and troubled debt restructurings.
+ References
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