Loans and Allowance - Summary of Non-Accrual Loans by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 51,289	$ 56,402
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	7,400	9,283
Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	26	30
Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	2,914	4,978
Real estate loans - Commercial and farm land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	25,003	28,095
Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	13,343	12,068
Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	2,433	1,667
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	170	117
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans		$ 164