Loans and Allowance for Loan Losses - Loans on Nonaccrual Status (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	$ 28,514	$ 27,796
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	16,978	16,349
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	372	472
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	5,148	5,622
Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	5,156	4,293
Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	551	711
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Nonaccrual Loans	$ 309	$ 349