Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 2,920,080	$ 2,902,209
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	657,764	622,579
Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	105,175	112,527
Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	101,909	98,639
Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	460,108	473,537
Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,272,761	1,266,682
Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	203,788	203,406
Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	79,258	75,748
Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,828	2,590
Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	37,489	46,501
Commercial Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	2,152,802	2,107,317
Commercial Pass | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	606,312	559,852
Commercial Pass | Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	104,928	112,209
Commercial Pass | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	87,384	85,728
Commercial Pass | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	140,813	145,402
Commercial Pass | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,164,325	1,148,561
Commercial Pass | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	10,034	9,092
Commercial Pass | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,695
Commercial Pass | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	37,311	46,473
Commercial Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	79,071	69,815
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	24,198	23,678
Commercial Special Mention | Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	214	224
Commercial Special Mention | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	7,880	1,384
Commercial Special Mention | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	1,468	5,437
Commercial Special Mention | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	44,639	38,199
Commercial Special Mention | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	663	893
Commercial Special Mention | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	9
Commercial Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans	110,276	140,553
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	25,352	34,460
Commercial Substandard | Agriculture production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	33	94
Commercial Substandard | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	6,253	11,356
Commercial Substandard | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	14,258	13,880
Commercial Substandard | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	63,212	79,078
Commercial Substandard | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	866	1,657
Commercial Substandard | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	133
Commercial Substandard | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	169	28
Commercial Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans	2,392	6,064
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	1,902	4,589
Commercial Doubtful | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	140	922
Commercial Doubtful | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	350	553
Commercial Doubtful | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	566,680	569,372
Consumer Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	296,399	301,614
Consumer Performing | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	191,023	189,721
Consumer Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	79,258	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	8,859	9,088
Consumer Non-Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	392	171
Consumer Non-Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	7,030	6,282
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 - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	1,202	2,043
Consumer Non-Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Non-Performing | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans		$ 301