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Allowance for Probable Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 | Sep. 30, 2011 | Dec. 31, 2011
Interest income recognized: |  |  |  |  |
Period of charge off for past due unsecured commercial loans |  |  | 90 days |  |
Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with related allowance | $ 32,856 |  | $ 32,856 |  | $ 87,369
Total impaired loans with no related allowance | 52,568 |  | 52,568 |  | 48,936
Unpaid principal balance: |  |  |  |  |
Total impaired loans with an allowance recorded | 36,090 |  | 36,090 |  | 87,419
Total impaired loans with no related allowance recorded | 53,776 |  | 53,776 |  | 51,423
Related Allowance | 17,791 |  | 17,791 |  | 27,252
Average recorded investment: |  |  |  |  |
Total impaired loans with an allowance recorded | 33,715 | 82,487 | 57,716 | 78,132 | 87,951
Total impaired loans with no related allowance recorded | 48,128 | 38,326 | 49,061 | 39,028 | 54,359
Interest income recognized: |  |  |  |  |
Total impaired loans with an allowance recorded | 33 | 204 | 98 | 637 | 858
Total impaired loans with no related allowance recorded | 64 | 150 | 244 | 207 | 399
Commercial | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with related allowance | 22,704 |  | 22,704 |  | 24,108
Total impaired loans with no related allowance | 812 |  | 812 |  | 3,495
Unpaid principal balance: |  |  |  |  |
Total impaired loans with an allowance recorded | 22,704 |  | 22,704 |  | 24,108
Total impaired loans with no related allowance recorded | 956 |  | 956 |  | 3,932
Related Allowance | 13,966 |  | 13,966 |  | 14,402
Average recorded investment: |  |  |  |  |
Total impaired loans with an allowance recorded | 22,729 | 23,007 | 22,517 | 23,036 | 24,145
Total impaired loans with no related allowance recorded | 840 | 572 | 538 | 459 | 3,942
Interest income recognized: |  |  |  |  |
Total impaired loans with an allowance recorded | 10 | 10 | 29 | 30 | 41
Total impaired loans with no related allowance recorded | 1 |  | 3 |  | 20
Commercial real estate: other construction and land development | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with related allowance | 3,671 |  | 3,671 |  | 34,417
Total impaired loans with no related allowance | 30,278 |  | 30,278 |  | 26,011
Unpaid principal balance: |  |  |  |  |
Total impaired loans with an allowance recorded | 3,671 |  | 3,671 |  | 34,432
Total impaired loans with no related allowance recorded | 30,417 |  | 30,417 |  | 26,112
Related Allowance | 568 |  | 568 |  | 3,073
Average recorded investment: |  |  |  |  |
Total impaired loans with an allowance recorded | 3,671 | 34,258 | 23,479 | 31,132 | 34,709
Total impaired loans with no related allowance recorded | 26,689 | 21,153 | 27,632 | 25,972 | 27,722
Interest income recognized: |  |  |  |  |
Total impaired loans with no related allowance recorded | 23 | 58 | 122 | 58 | 128
Commercial real estate: farmland and commercial | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with related allowance | 6,284 |  | 6,284 |  | 28,636
Total impaired loans with no related allowance | 14,598 |  | 14,598 |  | 13,595
Unpaid principal balance: |  |  |  |  |
Total impaired loans with an allowance recorded | 9,439 |  | 9,439 |  | 28,671
Total impaired loans with no related allowance recorded | 15,315 |  | 15,315 |  | 15,394
Related Allowance | 3,234 |  | 3,234 |  | 9,754
Average recorded investment: |  |  |  |  |
Total impaired loans with an allowance recorded | 7,117 | 24,833 | 11,518 | 22,759 | 28,883
Total impaired loans with no related allowance recorded | 14,069 | 11,686 | 14,850 | 7,487 | 16,271
Interest income recognized: |  |  |  |  |
Total impaired loans with an allowance recorded | 23 | 194 | 69 | 607 | 817
Total impaired loans with no related allowance recorded |  | 48 | 8 | 48 | 102
Commercial real estate: multifamily | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with no related allowance | 368 |  | 368 |  | 411
Unpaid principal balance: |  |  |  |  |
Total impaired loans with no related allowance recorded | 368 |  | 368 |  | 411
Average recorded investment: |  |  |  |  |
Total impaired loans with no related allowance recorded | 374 | 432 | 388 | 447 | 439
Residential: first lien | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with related allowance | 197 |  | 197 |  | 208
Total impaired loans with no related allowance | 3,290 |  | 3,290 |  | 2,082
Unpaid principal balance: |  |  |  |  |
Total impaired loans with an allowance recorded | 276 |  | 276 |  | 208
Total impaired loans with no related allowance recorded | 3,402 |  | 3,402 |  | 2,220
Related Allowance | 23 |  | 23 |  | 23
Average recorded investment: |  |  |  |  |
Total impaired loans with an allowance recorded | 198 | 389 | 202 | 1,205 | 214
Total impaired loans with no related allowance recorded | 2,957 | 1,470 | 2,485 | 1,720 | 2,230
Interest income recognized: |  |  |  |  |
Total impaired loans with no related allowance recorded | 15 | 10 | 31 | 15 | 27
Residential: junior lien | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with no related allowance | 1,857 |  | 1,857 |  | 1,962
Unpaid principal balance: |  |  |  |  |
Total impaired loans with no related allowance recorded | 1,950 |  | 1,950 |  | 1,970
Average recorded investment: |  |  |  |  |
Total impaired loans with no related allowance recorded | 1,836 | 1,725 | 1,958 | 1,749 | 1,980
Interest income recognized: |  |  |  |  |
Total impaired loans with no related allowance recorded | 25 | 34 | 79 | 86 | 118
Consumer | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with no related allowance | 1,273 |  | 1,273 |  | 1,334
Unpaid principal balance: |  |  |  |  |
Total impaired loans with no related allowance recorded | 1,276 |  | 1,276 |  | 1,338
Average recorded investment: |  |  |  |  |
Total impaired loans with no related allowance recorded | 1,271 | 1,288 | 1,149 | 1,192 | 1,729
Foreign | Class of financing receivable |  |  |  |  |
Recorded investment: |  |  |  |  |
Total impaired loans with no related allowance | 92 |  | 92 |  | 46
Unpaid principal balance: |  |  |  |  |
Total impaired loans with no related allowance recorded | 92 |  | 92 |  | 46
Average recorded investment: |  |  |  |  |
Total impaired loans with no related allowance recorded | 92 |  | 61 | 2 | 46
Interest income recognized: |  |  |  |  |
Total impaired loans with no related allowance recorded |  |  | $ 1 |  | $ 4

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