Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 3,616,627	$ 3,632,409
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	787,390	761,705
Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	99,226	114,348
Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	155,117	177,082
Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,606,735	1,611,809
Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	626,202	616,385
Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	256,790	255,223
Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	61,742	69,783
Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,378	1,545
Other loans
Financing Receivable, Recorded Investment [Line Items]
Loans	22,047	24,529
Commercial Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	2,596,596	2,635,448
Commercial Pass | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	724,556	708,835
Commercial Pass | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	86,358	114,318
Commercial Pass | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	142,676	162,976
Commercial Pass | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,466,354	1,473,714
Commercial Pass | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	147,361	143,657
Commercial Pass | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	6,011	6,194
Commercial Pass | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,256	1,420
Commercial Pass | Other loans
Financing Receivable, Recorded Investment [Line Items]
Loans	22,024	24,334
Commercial Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	65,160	72,407
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	10,148	11,332
Commercial Special Mention | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	376
Commercial Special Mention | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	1,123	1,132
Commercial Special Mention | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	50,952	57,676
Commercial Special Mention | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	2,229	2,232
Commercial Special Mention | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	332	35
Commercial Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans	175,537	146,254
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	52,172	41,013
Commercial Substandard | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	12,492	30
Commercial Substandard | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	11,116	12,029
Commercial Substandard | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	89,188	80,184
Commercial Substandard | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	9,444	11,494
Commercial Substandard | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	980	1,184
Commercial Substandard | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	122	125
Commercial Substandard | Other loans
Financing Receivable, Recorded Investment [Line Items]
Loans	23	195
Commercial Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans	650	661
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	514	525
Commercial Doubtful | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	136	136
Consumer Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	764,379	764,261
Consumer Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	455,612	448,494
Consumer Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	247,169	246,101
Consumer Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	61,598	69,666
Consumer Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	14,305	13,378
Consumer Non-Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	202	945
Consumer Non-Performing | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	241	235
Consumer Non-Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	11,420	10,372
Consumer Non-Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	2,298	1,709
Consumer Non-Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 144	$ 117