Investment Securities (Schedule of Gross Pre-Tax Unrealized Losses on Investment Securities) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	$ 12,914	$ 27,220
Available for sale, Gross Unrealized Losses Less than 12 months	42	580
Available for sale, Fair Value 12 months or longer	18,979	13,764
Available for sale, Gross Unrealized Losses 12 months or longer	462	567
Available for sale, Fair Value Total	31,893	40,984
Available for sale, Gross Unrealized Losses Total	504	1,147
Held to maturity, Fair Value Less than 12 months	1,279	7,813
Held to maturity, Gross Unrealized Losses Less than 12 months	7	480
Held to maturity, Fair Value 12 months or longer	5,991	1,068
Held to maturity, Gross Unrealized Losses 12 months or longer	248	54
Held to maturity, Fair Value Total	7,270	8,881
Held to maturity, Gross Unrealized Losses Total	255	534
Asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	897	7,540
Available for sale, Gross Unrealized Losses Less than 12 months	4	58
Available for sale, Fair Value 12 months or longer	8,858	9,002
Available for sale, Gross Unrealized Losses 12 months or longer	217	365
Available for sale, Fair Value Total	9,755	16,542
Available for sale, Gross Unrealized Losses Total	221	423
Held to maturity, Fair Value Less than 12 months	443	1,649
Held to maturity, Gross Unrealized Losses Less than 12 months	2	11
Held to maturity, Fair Value 12 months or longer	0	29
Held to maturity, Gross Unrealized Losses 12 months or longer	0	1
Held to maturity, Fair Value Total	443	1,678
Held to maturity, Gross Unrealized Losses Total	2	12
US Treasury and federal agencies, direct obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	4,374	182
Available for sale, Gross Unrealized Losses Less than 12 months	3	1
Available for sale, Fair Value 12 months or longer	158	113
Available for sale, Gross Unrealized Losses 12 months or longer	1	1
Available for sale, Fair Value Total	4,532	295
Available for sale, Gross Unrealized Losses Total	4	2
Held to maturity, Fair Value Less than 12 months	114	4,571
Held to maturity, Gross Unrealized Losses Less than 12 months	1	448
Held to maturity, Fair Value 12 months or longer	4,781	0
Held to maturity, Gross Unrealized Losses 12 months or longer	221	0
Held to maturity, Fair Value Total	4,895	4,571
Held to maturity, Gross Unrealized Losses Total	222	448
US Treasury and federal agencies, mortgage-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	3,391	10,562
Available for sale, Gross Unrealized Losses Less than 12 months	23	316
Available for sale, Fair Value 12 months or longer	7,026	2,389
Available for sale, Gross Unrealized Losses 12 months or longer	175	76
Available for sale, Fair Value Total	10,417	12,951
Available for sale, Gross Unrealized Losses Total	198	392
Asset-backed securities, student loans
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	291	1,930
Available for sale, Gross Unrealized Losses Less than 12 months	2	16
Available for sale, Fair Value 12 months or longer	6,158	7,252
Available for sale, Gross Unrealized Losses 12 months or longer	120	252
Available for sale, Fair Value Total	6,449	9,182
Available for sale, Gross Unrealized Losses Total	122	268
Held to maturity, Fair Value Less than 12 months	364	1,352
Held to maturity, Gross Unrealized Losses Less than 12 months	1	10
Held to maturity, Fair Value 12 months or longer	0	0
Held to maturity, Gross Unrealized Losses 12 months or longer	0	0
Held to maturity, Fair Value Total	364	1,352
Held to maturity, Gross Unrealized Losses Total	1	10
Asset-backed securities, credit cards
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	0	3,714
Available for sale, Gross Unrealized Losses Less than 12 months	0	30
Available for sale, Fair Value 12 months or longer	1,258	161
Available for sale, Gross Unrealized Losses 12 months or longer	30	11
Available for sale, Fair Value Total	1,258	3,875
Available for sale, Gross Unrealized Losses Total	30	41
Held to maturity, Fair Value Less than 12 months		297
Held to maturity, Gross Unrealized Losses Less than 12 months		1
Held to maturity, Fair Value 12 months or longer		29
Held to maturity, Gross Unrealized Losses 12 months or longer		1
Held to maturity, Fair Value Total		326
Held to maturity, Gross Unrealized Losses Total		2
Asset-backed securities, sub-prime
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	0	0
Available for sale, Gross Unrealized Losses Less than 12 months	0	0
Available for sale, Fair Value 12 months or longer	936	1,150
Available for sale, Gross Unrealized Losses 12 months or longer	59	91
Available for sale, Fair Value Total	936	1,150
Available for sale, Gross Unrealized Losses Total	59	91
Asset-backed securities, other
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	606	1,896
Available for sale, Gross Unrealized Losses Less than 12 months	2	12
Available for sale, Fair Value 12 months or longer	506	439
Available for sale, Gross Unrealized Losses 12 months or longer	8	11
Available for sale, Fair Value Total	1,112	2,335
Available for sale, Gross Unrealized Losses Total	10	23
Held to maturity, Fair Value Less than 12 months	79
Held to maturity, Gross Unrealized Losses Less than 12 months	1
Held to maturity, Fair Value 12 months or longer	0
Held to maturity, Gross Unrealized Losses 12 months or longer	0
Held to maturity, Fair Value Total	79
Held to maturity, Gross Unrealized Losses Total	1
Total non-U.S. debt securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	2,591	3,074
Available for sale, Gross Unrealized Losses Less than 12 months	3	12
Available for sale, Fair Value 12 months or longer	543	424
Available for sale, Gross Unrealized Losses 12 months or longer	8	10
Available for sale, Fair Value Total	3,134	3,498
Available for sale, Gross Unrealized Losses Total	11	22
Held to maturity, Fair Value Less than 12 months	255	834
Held to maturity, Gross Unrealized Losses Less than 12 months	1	3
Held to maturity, Fair Value 12 months or longer	658	878
Held to maturity, Gross Unrealized Losses 12 months or longer	15	45
Held to maturity, Fair Value Total	913	1,712
Held to maturity, Gross Unrealized Losses Total	16	48
Non-U.S. debt securities, mortgage-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	443	868
Available for sale, Gross Unrealized Losses Less than 12 months	1	2
Available for sale, Fair Value 12 months or longer	176	258
Available for sale, Gross Unrealized Losses 12 months or longer	1	7
Available for sale, Fair Value Total	619	1,126
Available for sale, Gross Unrealized Losses Total	2	9
Held to maturity, Fair Value Less than 12 months	255
Held to maturity, Gross Unrealized Losses Less than 12 months	1
Held to maturity, Fair Value 12 months or longer	658
Held to maturity, Gross Unrealized Losses 12 months or longer	15
Held to maturity, Fair Value Total	913
Held to maturity, Gross Unrealized Losses Total	16
Non-U.S. debt securities, asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	0	551
Available for sale, Gross Unrealized Losses Less than 12 months	0	1
Available for sale, Fair Value 12 months or longer	84	16
Available for sale, Gross Unrealized Losses 12 months or longer	1	1
Available for sale, Fair Value Total	84	567
Available for sale, Gross Unrealized Losses Total	1	2
Non-U.S. debt securities, other
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	2,148	1,655
Available for sale, Gross Unrealized Losses Less than 12 months	2	9
Available for sale, Fair Value 12 months or longer	283	150
Available for sale, Gross Unrealized Losses 12 months or longer	6	2
Available for sale, Fair Value Total	2,431	1,805
Available for sale, Gross Unrealized Losses Total	8	11
State and political subdivisions
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	439	3,242
Available for sale, Gross Unrealized Losses Less than 12 months	2	113
Available for sale, Fair Value 12 months or longer	1,786	1,268
Available for sale, Gross Unrealized Losses 12 months or longer	42	85
Available for sale, Fair Value Total	2,225	4,510
Available for sale, Gross Unrealized Losses Total	44	198
Collateralized mortgage obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	886	1,581
Available for sale, Gross Unrealized Losses Less than 12 months	5	55
Available for sale, Fair Value 12 months or longer	314	510
Available for sale, Gross Unrealized Losses 12 months or longer	10	21
Available for sale, Fair Value Total	1,200	2,091
Available for sale, Gross Unrealized Losses Total	15	76
Held to maturity, Fair Value Less than 12 months	467	759
Held to maturity, Gross Unrealized Losses Less than 12 months	3	18
Held to maturity, Fair Value 12 months or longer	552	161
Held to maturity, Gross Unrealized Losses 12 months or longer	12	8
Held to maturity, Fair Value Total	1,019	920
Held to maturity, Gross Unrealized Losses Total	15	26
Other U.S. debt securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	336	1,039
Available for sale, Gross Unrealized Losses Less than 12 months	2	25
Available for sale, Fair Value 12 months or longer	294	58
Available for sale, Gross Unrealized Losses 12 months or longer	9	9
Available for sale, Fair Value Total	630	1,097
Available for sale, Gross Unrealized Losses Total	$ 11	$ 34