Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 6) (USD $)	12 Months Ended
	Dec. 31, 2012 contract	Dec. 31, 2011 contract
Troubled debt restructured loans
Additions to TDR loans	$ 78,800,000
Payment received on TDR Loans	61,300,000
Charge-offs on TDR Loans	15,500,000
Commitments to lend additional funds on restructured loans	3,700,000
Total Troubled Debt Restructured Loans That Subsequently Defaulted
Troubled debt restructured loans
Number of contracts	9	3
Period-End Outstanding Principal	14,911,000	6,384,000
Period-End Specific Reserve	300,000	1,000
Commercial
Troubled debt restructured loans
Number of contracts	6	1
Period-End Outstanding Principal	689,000	45,000
Period-End Specific Reserve	300,000	1,000
Number of loans paid off	4
Commercial real estate mortgages
Troubled debt restructured loans
Number of contracts	1
Period-End Outstanding Principal	13,802,000
Land
Troubled debt restructured loans
Number of contracts	2	2
Period-End Outstanding Principal	$ 420,000	$ 6,339,000
Number of loans charged-off	1