Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 3,722,733	$ 3,632,409
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	857,844	761,705
Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	102,270	114,348
Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	165,388	177,082
Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,621,436	1,611,809
Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	629,162	616,385
Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	261,811	255,223
Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	61,533	69,783
Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,231	1,545
Other loans
Financing Receivable, Recorded Investment [Line Items]
Loans	22,058	24,529
Commercial Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	2,684,906	2,635,448
Commercial Pass | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	794,840	708,835
Commercial Pass | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	85,965	114,318
Commercial Pass | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	141,902	162,976
Commercial Pass | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	1,488,792	1,473,714
Commercial Pass | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	144,005	143,657
Commercial Pass | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	6,240	6,194
Commercial Pass | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	1,115	1,420
Commercial Pass | Other loans
Financing Receivable, Recorded Investment [Line Items]
Loans	22,047	24,334
Commercial Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	65,809	72,407
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	14,787	11,332
Commercial Special Mention | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	1,780
Commercial Special Mention | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	1,060	1,132
Commercial Special Mention | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	45,513	57,676
Commercial Special Mention | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	2,377	2,232
Commercial Special Mention | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	292	35
Commercial Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans	169,305	146,254
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	47,917	41,013
Commercial Substandard | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	14,525	30
Commercial Substandard | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	10,893	12,029
Commercial Substandard | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	86,896	80,184
Commercial Substandard | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	8,153	11,494
Commercial Substandard | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	794	1,184
Commercial Substandard | Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment [Line Items]
Loans	116	125
Commercial Substandard | Other loans
Financing Receivable, Recorded Investment [Line Items]
Loans	11	195
Commercial Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans	300	661
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	300	525
Commercial Doubtful | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans		136
Consumer Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	787,311	764,261
Consumer Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	11,368
Consumer Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	462,455	448,494
Consumer Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	252,130	246,101
Consumer Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	61,358	69,666
Consumer Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	15,102	13,378
Consumer Non-Performing | Real estate loans - Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	165	945
Consumer Non-Performing | Real estate loans - Commercial and farm land
Financing Receivable, Recorded Investment [Line Items]
Loans	235	235
Consumer Non-Performing | Real estate loans - Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	12,172	10,372
Consumer Non-Performing | Real estate loans - Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	2,355	1,709
Consumer Non-Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 175	$ 117