Loans and Allowance for Loan Losses - Loans on Nonaccrual Status (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	$ 27,796	$ 34,471
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	16,349	21,512
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	472	1,072
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	5,622	6,551
Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	4,293	4,365
Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	711	711
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	$ 349	$ 260