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Allowance for Probable Loan Losses (Non-accrual Basis By Loan Class) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | $ 37,245,000 | $ 47,685,000 | $ 63,559,000
Reduced interest income on non-accrual loans | 2,461,800 | 3,298,000 | $ 4,013,000
Commercial |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 22,369,000 | 30,894,000 |
Commercial Real Estate: Other Construction and Land Development |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 4,776,000 | 3,668,000 |
Commercial Real Estate: Farmland & Commercial |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 8,314,000 | 11,543,000 |
Commercial Real Estate: Multifamily |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 552,000 | 777,000 |
Residential First Lien |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 655,000 | 383,000 |
Residential Junior Lien |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 166,000 | 21,000 |
Consumer |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 26,000 | 34,000 |
Foreign |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | $ 387,000 | $ 365,000 |

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- Definition Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Recorded Investment -URI http://asc.fasb.org/extlink&oid=65880944 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524 + Details
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