Investment Securities (Schedule Of Contractual Maturities Of Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	$ 7,450
Available for sale, 1 to 5 Years	40,511
Available for sale, 6 to 10 Years	20,987
Available for sale, Over 10 Years	33,490
Held to maturity, Under 1 Year	454
Held to maturity, 1 to 5 Years	2,968
Held to maturity, 6 to 10 Years	5,846
Held to maturity, Over 10 Years	4,325
Total asset-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	2,469
Available for sale, 1 to 5 Years	14,797
Available for sale, 6 to 10 Years	8,883
Available for sale, Over 10 Years	5,030
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	356
Held to maturity, 6 to 10 Years	568
Held to maturity, Over 10 Years	334
US Treasury and federal agencies, direct obligations
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	3
Available for sale, 1 to 5 Years	40
Available for sale, 6 to 10 Years	62
Available for sale, Over 10 Years	699
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	0
Held to maturity, 6 to 10 Years	5,000
Held to maturity, Over 10 Years	0
US Treasury and federal agencies, mortgage-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	117
Available for sale, 1 to 5 Years	2,335
Available for sale, 6 to 10 Years	6,039
Available for sale, Over 10 Years	20,254
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	30
Held to maturity, 6 to 10 Years	28
Held to maturity, Over 10 Years	73
Asset-backed securities, student loans
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	746
Available for sale, 1 to 5 Years	6,797
Available for sale, 6 to 10 Years	4,976
Available for sale, Over 10 Years	3,147
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	92
Held to maturity, 6 to 10 Years	92
Held to maturity, Over 10 Years	327
Asset-backed securities, credit cards
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	1,578
Available for sale, 1 to 5 Years	5,775
Available for sale, 6 to 10 Years	2,315
Available for sale, Over 10 Years	0
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	0
Held to maturity, 6 to 10 Years	25
Held to maturity, Over 10 Years	0
Asset-backed securities, sub-prime
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	28
Available for sale, 1 to 5 Years	29
Available for sale, 6 to 10 Years	4
Available for sale, Over 10 Years	1,324
Asset-backed securities, other
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	117
Available for sale, 1 to 5 Years	2,196
Available for sale, 6 to 10 Years	1,588
Available for sale, Over 10 Years	559
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	264
Held to maturity, 6 to 10 Years	451
Held to maturity, Over 10 Years	7
Total non-U.S. debt securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	3,783
Available for sale, 1 to 5 Years	14,081
Available for sale, 6 to 10 Years	913
Available for sale, Over 10 Years	5,198
Held to maturity, Under 1 Year	262
Held to maturity, 1 to 5 Years	1,369
Held to maturity, 6 to 10 Years	46
Held to maturity, Over 10 Years	2,938
Non-U.S. debt securities, mortgage-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	256
Available for sale, 1 to 5 Years	5,503
Available for sale, 6 to 10 Years	156
Available for sale, Over 10 Years	4,980
Held to maturity, Under 1 Year	97
Held to maturity, 1 to 5 Years	590
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	2,930
Non-U.S. debt securities, asset-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	288
Available for sale, 1 to 5 Years	4,907
Available for sale, 6 to 10 Years	335
Available for sale, Over 10 Years	218
Held to maturity, Under 1 Year	150
Held to maturity, 1 to 5 Years	626
Held to maturity, 6 to 10 Years	46
Held to maturity, Over 10 Years	0
Non-US debt securities, government securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	1,917
Available for sale, 1 to 5 Years	1,044
Available for sale, 6 to 10 Years	0
Available for sale, Over 10 Years	0
Held to maturity, Under 1 Year	15
Held to maturity, 1 to 5 Years	0
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	0
Non-U.S. debt securities, other
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	1,322
Available for sale, 1 to 5 Years	2,627
Available for sale, 6 to 10 Years	422
Available for sale, Over 10 Years	0
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	153
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	8
State and political subdivisions
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	714
Available for sale, 1 to 5 Years	3,064
Available for sale, 6 to 10 Years	2,739
Available for sale, Over 10 Years	1,083
Held to maturity, Under 1 Year	52
Held to maturity, 1 to 5 Years	18
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	0
Collateralized mortgage obligations
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	148
Available for sale, 1 to 5 Years	2,265
Available for sale, 6 to 10 Years	1,223
Available for sale, Over 10 Years	1,192
Held to maturity, Under 1 Year	140
Held to maturity, 1 to 5 Years	1,195
Held to maturity, 6 to 10 Years	204
Held to maturity, Over 10 Years	980
Other U.S.debt securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, Under 1 Year	216
Available for sale, 1 to 5 Years	3,929
Available for sale, 6 to 10 Years	1,128
Available for sale, Over 10 Years	$ 34