Loans And Allowance For Loan Losses (Narrative) (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Loans And Allowance For Loan Losses [Abstract]
Restructed Loans on NonAccrual Status	$ 27,500,000
Loans pledged at the Federal Home Loan Bank as collateral for borrowings and letters of credit obtained to secure public deposits	3,200,000,000
Loans pledged at the Federal Reserve Bank as collateral for discount window borrowings	1,200,000,000
Restructured loans performing under their modified terms	44,400,000		41,300,000
Aggregate restructured credit card loans held	15,400,000		22,400,000
Personal real estate loans excluded from table	225,600,000		222,800,000
Consumer loans excluded from table	127,100,000		148,700,000
Consumer and personal real estate loans excluded from table, as a percentage of Personal Banking portfolio	8.80%		9.80%
Period after which loans are deemed in default (in days)	90 days
Effect on Interest Income Resulting From Modification to Credit Card Loans		2,600,000
Commitments to lend additional funds to customers with restructured loans	12,900,000
Foreclosed real estate	18,200,000		18,300,000
Personal property acquired in repossession	$ 2,000,000		$ 4,200,000