Net Interest Revenue (Components Of Interest Revenue And Interest Expenses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net Interest Revenue [Abstract]
Deposits with banks	$ 31	$ 42
U.S. Treasury and federal agencies	194	199
State and political subdivisions	51	54
Other investments	341	405
Securities purchased under resale agreements	13	9
Loans and leases	56	55
Other interest-earning assets	1	1
Total interest revenue	687	765
Deposits	34	53
Short-term borrowings	16	18
Long-term debt	56	66
Other interest-bearing liabilities	5	3
Total interest expense	111	140
Net interest revenue	$ 576	$ 625