Investment Securities (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Organizaion Securities Banks	Sep. 30, 2012	Sep. 30, 2013 Securities Banks	Sep. 30, 2012	Dec. 31, 2012 Securities
Investment [Line Items]
Number of HTM investment securities in an unrealized loss position	207		207		84
Number of AFS investment securities in an unrealized loss position	258		258		256
Number of banks in CDO pools current following deferral period	107		107
Number of banks in CDO pools remaining in deferral	158		158
Number of NRSRO Ratings	1
Nontaxable interest income on securities	$ 3,400,000	$ 4,200,000	$ 10,100,000	$ 13,700,000
Carrying value of pledged securities	$ 1,500,000,000		$ 1,500,000,000
Municipal Securities [Member] | Minimum [Member]
Investment [Line Items]
Investment term of maturity, in years			1
Municipal Securities [Member] | Maximum [Member]
Investment [Line Items]
Investment term of maturity, in years			25