Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 2,925,457	$ 2,902,209
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	652,356	622,579
Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	98,489	112,527
Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	149,875	98,639
Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,264,180	1,266,682
Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	452,277	473,537
Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	206,816	203,406
Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	70,380	75,748
Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,815	2,590
Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	29,269	46,501
Commercial Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	2,184,228	2,107,317
Commercial Pass | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	603,166	559,852
Commercial Pass | Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	98,458	112,209
Commercial Pass | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	142,169	85,728
Commercial Pass | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,163,570	1,148,561
Commercial Pass | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	139,481	145,402
Commercial Pass | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	6,633	9,092
Commercial Pass | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,688
Commercial Pass | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	29,063	46,473
Commercial Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	64,798	69,815
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	18,481	23,678
Commercial Special Mention | Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans		224
Commercial Special Mention | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	2,752	1,384
Commercial Special Mention | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	41,954	38,199
Commercial Special Mention | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	1,504	5,437
Commercial Special Mention | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	105	893
Commercial Special Mention | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	2
Commercial Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans	104,246	140,553
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	29,155	34,460
Commercial Substandard | Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	31	94
Commercial Substandard | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	4,491	11,356
Commercial Substandard | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	58,309	79,078
Commercial Substandard | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	10,803	13,880
Commercial Substandard | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	1,126	1,657
Commercial Substandard | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	127
Commercial Substandard | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	204	28
Commercial Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans	1,806	6,064
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	1,554	4,589
Commercial Doubtful | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	112	553
Commercial Doubtful | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	140	922
Commercial Doubtful | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	561,390	569,372
Consumer Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	293,329	301,614
Consumer Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	197,776	189,721
Consumer Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	70,285	75,748
Consumer Performing | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans		2,289
Consumer Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	8,989	9,088
Consumer Non-Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	463	171
Consumer Non-Performing | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	235	291
Consumer Non-Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	7,020	6,282
Consumer Non-Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	1,176	2,043
Consumer Non-Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	95
Consumer Non-Performing | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans		$ 301