Net Interest Revenue (Components Of Interest Revenue And Interest Expenses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Interest Revenue [Abstract]
Deposits with banks	$ 31	$ 39	$ 108	$ 94
U.S. Treasury and federal agencies	200	186	605	590
State and political subdivisions	53	55	161	166
Other investments	374	374	1,185	1,093
Securities purchased under resale agreements	15	6	37	22
Loans and leases	57	68	183	215
Other interest-earning assets	0	0	2	1
Total interest revenue	730	728	2,281	2,181
Deposits	37	52	127	154
Short-term borrowings	18	23	55	74
Long-term debt	52	73	172	220
Other interest-bearing liabilities	4	2	11	6
Total interest expense	111	150	365	454
Net interest revenue	$ 619	$ 578	$ 1,916	$ 1,727