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Loans and Allowance for Loan Losses Loans and Allowance for Loan Losses - Allowance (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012 alternative | Dec. 31, 2011 | Dec. 31, 2010
Financing Receivable, Impaired [Line Items] |  |  |
Minimum balance of adversely classified loan in which a detailed analysis is performed | $ 100 |  |
Number of alternatives for measuring impaired loans receivable | 3 |  |
Time Period Used Base For Loss Estimations | five-year |  |
Balance, beginning of year | 11,120 | 10,393 | 9,462
Provision charged to expense | 2,647 | 3,101 | 3,737
Losses charged off | (2,371) | (3,760) | (3,122)
Recoveries | 380 | 1,386 | 316
Balance, end of period | 11,776 | 11,120 | 10,393
Individually evaluated for impairment | 511 | 575 | 1,086
Collectively evaluated for impairment | 11,265 | 10,545 | 9,307
Ending balance | 911,065 | 860,074 | 804,581
Individually evaluated for impairment | 6,564 | 5,868 | 8,484
Collectively evaluated for impairment | 904,501 | 854,206 | 796,097
Unsecured Open-end Loans [Member] |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Period When Loans Are Charged Down | 180 days |  |
Other Secured Loans [Member] |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Period When Loans Are Charged Down | 120 days |  |
Commercial/Commercial Real Estate [Member] |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Balance, beginning of year | 8,791 | 8,307 | 7,428
Provision charged to expense | 1,979 | 2,309 | 3,473
Losses charged off | (1,586) | (3,077) | (2,770)
Recoveries | 117 | 1,252 | 176
Balance, end of period | 9,301 | 8,791 | 8,307
Individually evaluated for impairment | 457 | 575 | 1,086
Collectively evaluated for impairment | 8,844 | 8,216 | 7,221
Ending balance | 569,717 | 505,693 | 465,390
Individually evaluated for impairment | 5,334 | 4,719 | 7,332
Collectively evaluated for impairment | 564,383 | 500,974 | 458,058
Agriculture/Agricultural Real Estate [Member] |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Balance, beginning of year | 546 | 404 | 315
Provision charged to expense | (47) | 205 | 89
Losses charged off | (12) | (66) | (3)
Recoveries | 71 | 3 | 3
Balance, end of period | 558 | 546 | 404
Individually evaluated for impairment | 54 | 0 | 0
Collectively evaluated for impairment | 504 | 546 | 404
Ending balance | 145,695 | 130,595 | 118,973
Individually evaluated for impairment | 1,230 | 1,149 | 1,152
Collectively evaluated for impairment | 144,465 | 129,446 | 117,821
Residential Real Estate [Member] |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Balance, beginning of year | 636 | 440 | 488
Provision charged to expense | 580 | 546 | (118)
Losses charged off | (524) | (363) | (65)
Recoveries | 34 | 13 | 135
Balance, end of period | 726 | 636 | 440
Individually evaluated for impairment | 0 | 0 | 0
Collectively evaluated for impairment | 726 | 636 | 440
Ending balance | 179,309 | 185,151 | 183,000
Individually evaluated for impairment | 0 | 0 | 0
Collectively evaluated for impairment | 179,309 | 185,151 | 183,000
1-4 Family residential properties |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Period When Loans Are Charged Down | 180 days |  |
Consumer loans |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Balance, beginning of year | 378 | 392 | 410
Provision charged to expense | 116 | 122 | 264
Losses charged off | (249) | (254) | (284)
Recoveries | 158 | 118 | 2
Balance, end of period | 403 | 378 | 392
Individually evaluated for impairment | 0 | 0 | 0
Collectively evaluated for impairment | 403 | 378 | 392
Ending balance | 16,066 | 16,270 | 20,486
Individually evaluated for impairment | 0 | 0 | 0
Collectively evaluated for impairment | 16,066 | 16,270 | 20,486
Unallocated [Member] |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Balance, beginning of year | 769 | 850 | 821
Provision charged to expense | 19 | (81) | 29
Losses charged off | 0 | 0 | 0
Recoveries | 0 | 0 | 0
Balance, end of period | 788 | 769 | 850
Individually evaluated for impairment | 0 | 0 | 0
Collectively evaluated for impairment | 788 | 769 | 850
Ending balance | 278 | 22,365 | 16,732
Individually evaluated for impairment | 0 | 0 | 0
Collectively evaluated for impairment | $ 278 | $ 22,365 | $ 16,732

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- Definition Amount net of deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References No definition available. + Details
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- Definition Minimum balance of adversely classified loan in which a detailed analysis is performed. + References No definition available. + Details
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- Definition Number of alternatives for measuring impaired loans receivable. + References No definition available. + Details
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- Definition The amount of time when past due loans receivable are written-off. + References No definition available. + Details
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- Definition Time period used a a base for loss estimations. + References No definition available. + Details
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- Definition Reflects the gross amount charged against earnings during the period as credit losses (bad debt expense) based on review of the loan and lease portfolio and application of the methodology for estimating credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 114 -Paragraph 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph d -Article 9 + Details
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- Definition Reflects the amount of loans and leases that have been removed, or charged off, from both loan receivables and the reserve for credit losses, typically because they are considered to be not salvageable or have been purchased by unconsolidated collection entities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 114 -Paragraph 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph d -Article 9 + Details
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- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524 + Details
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- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524 + Details
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- Definition Amount of recovery of financing receivables doubtful of collection that were previously charged off. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524 + Details
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- Definition Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 8, 9 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(1)(ii) -URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher OTS -Name Federal Regulation (FR) -Number Title 12 -Section 563c.102 -Paragraph 8 -Subparagraph a(ii) -Chapter V -Subsection I -LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph d -Article 9 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 114 -Paragraph 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section L -Subsection 1 + Details
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