Loans and Allowance - Summary of Non-Accrual Loans by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 56,402	$ 53,399
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	9,283	12,195
Agriculture Production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	30
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	4,978	4,814
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	28,095	22,612
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	12,068	11,476
Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,667	1,997
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	117
Finance Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans		301
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 164	$ 4