Investment Securities (Schedule of Gross Pre-Tax Unrealized Losses on Investment Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	$ 23,650	$ 27,220
Available for sale, Gross Unrealized Losses Less than 12 months	348	580
Available for sale, Fair Value 12 months or longer	14,768	13,764
Available for sale, Gross Unrealized Losses 12 months or longer	503	567
Available for sale, Fair Value Total	38,418	40,984
Available for sale, Gross Unrealized Losses Total	851	1,147
Held to maturity, Fair Value Less than 12 months	6,678	7,813
Held to maturity, Gross Unrealized Losses Less than 12 months	343	480
Held to maturity, Fair Value 12 months or longer	1,408	1,068
Held to maturity, Gross Unrealized Losses 12 months or longer	42	54
Held to maturity, Fair Value Total	8,086	8,881
Held to maturity, Gross Unrealized Losses Total	385	534
Asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	5,914	7,540
Available for sale, Gross Unrealized Losses Less than 12 months	41	58
Available for sale, Fair Value 12 months or longer	9,009	9,002
Available for sale, Gross Unrealized Losses 12 months or longer	301	365
Available for sale, Fair Value Total	14,923	16,542
Available for sale, Gross Unrealized Losses Total	342	423
Held to maturity, Fair Value Less than 12 months	426	1,649
Held to maturity, Gross Unrealized Losses Less than 12 months	2	11
Held to maturity, Fair Value 12 months or longer	176	29
Held to maturity, Gross Unrealized Losses 12 months or longer	1	1
Held to maturity, Fair Value Total	602	1,678
Held to maturity, Gross Unrealized Losses Total	3	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	1,433	182
Available for sale, Gross Unrealized Losses Less than 12 months	5	1
Available for sale, Fair Value 12 months or longer	130	113
Available for sale, Gross Unrealized Losses 12 months or longer	1	1
Available for sale, Fair Value Total	1,563	295
Available for sale, Gross Unrealized Losses Total	6	2
Held to maturity, Fair Value Less than 12 months	4,751	4,571
Held to maturity, Gross Unrealized Losses Less than 12 months	328	448
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	4,751	4,571
Held to maturity, Gross Unrealized Losses Total	328	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	9,475	10,562
Available for sale, Gross Unrealized Losses Less than 12 months	197	316
Available for sale, Fair Value 12 months or longer	3,161	2,389
Available for sale, Gross Unrealized Losses 12 months or longer	93	76
Available for sale, Fair Value Total	12,636	12,951
Available for sale, Gross Unrealized Losses Total	290	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	606	1,930
Available for sale, Gross Unrealized Losses Less than 12 months	5	16
Available for sale, Fair Value 12 months or longer	7,271	7,252
Available for sale, Gross Unrealized Losses 12 months or longer	198	252
Available for sale, Fair Value Total	7,877	9,182
Available for sale, Gross Unrealized Losses Total	203	268
Held to maturity, Fair Value Less than 12 months	297		1,352
Held to maturity, Gross Unrealized Losses Less than 12 months	1	10
Held to maturity, Fair Value 12 months or longer	176		0
Held to maturity, Gross Unrealized Losses 12 months or longer	1	0
Held to maturity, Fair Value Total	473		1,352
Held to maturity, Gross Unrealized Losses Total	2	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	3,311	3,714
Available for sale, Gross Unrealized Losses Less than 12 months	26	30
Available for sale, Fair Value 12 months or longer	214	161
Available for sale, Gross Unrealized Losses 12 months or longer	11	11
Available for sale, Fair Value Total	3,525	3,875
Available for sale, Gross Unrealized Losses Total	37	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	1,106	1,150
Available for sale, Gross Unrealized Losses 12 months or longer	82	91
Available for sale, Fair Value Total	1,106	1,150
Available for sale, Gross Unrealized Losses Total	82	91
Asset-backed securities, other
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	1,997	1,896
Available for sale, Gross Unrealized Losses Less than 12 months	10	12
Available for sale, Fair Value 12 months or longer	418	439
Available for sale, Gross Unrealized Losses 12 months or longer	10	11
Available for sale, Fair Value Total	2,415	2,335
Available for sale, Gross Unrealized Losses Total	20	23
Held to maturity, Fair Value Less than 12 months	129
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	129
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	2,751	3,074
Available for sale, Gross Unrealized Losses Less than 12 months	9	12
Available for sale, Fair Value 12 months or longer	546	424
Available for sale, Gross Unrealized Losses 12 months or longer	9	10
Available for sale, Fair Value Total	3,297	3,498
Available for sale, Gross Unrealized Losses Total	18	22
Held to maturity, Fair Value Less than 12 months		834
Held to maturity, Gross Unrealized Losses Less than 12 months		3
Held to maturity, Fair Value 12 months or longer		878
Held to maturity, Gross Unrealized Losses 12 months or longer		45
Held to maturity, Fair Value Total		1,712
Held to maturity, Gross Unrealized Losses Total		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	819	868
Available for sale, Gross Unrealized Losses Less than 12 months	2	2
Available for sale, Fair Value 12 months or longer	326	258
Available for sale, Gross Unrealized Losses 12 months or longer	5	7
Available for sale, Fair Value Total	1,145	1,126
Available for sale, Gross Unrealized Losses Total	7	9
Held to maturity, Fair Value Less than 12 months	906
Held to maturity, Gross Unrealized Losses Less than 12 months	2
Held to maturity, Fair Value 12 months or longer	825
Held to maturity, Gross Unrealized Losses 12 months or longer	27
Held to maturity, Fair Value Total	1,731
Held to maturity, Gross Unrealized Losses Total	29
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	280	551
Available for sale, Gross Unrealized Losses Less than 12 months	1	1
Available for sale, Fair Value 12 months or longer	71	16
Available for sale, Gross Unrealized Losses 12 months or longer	1	1
Available for sale, Fair Value Total	351	567
Available for sale, Gross Unrealized Losses Total	2	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	1,652	1,655
Available for sale, Gross Unrealized Losses Less than 12 months	6	9
Available for sale, Fair Value 12 months or longer	149	150
Available for sale, Gross Unrealized Losses 12 months or longer	3	2
Available for sale, Fair Value Total	1,801	1,805
Available for sale, Gross Unrealized Losses Total	9	11
State and political subdivisions
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	1,850	3,242
Available for sale, Gross Unrealized Losses Less than 12 months	49	113
Available for sale, Fair Value 12 months or longer	1,311	1,268
Available for sale, Gross Unrealized Losses 12 months or longer	68	85
Available for sale, Fair Value Total	3,161	4,510
Available for sale, Gross Unrealized Losses Total	117	198
Collateralized mortgage obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	1,444	1,581
Available for sale, Gross Unrealized Losses Less than 12 months	34	55
Available for sale, Fair Value 12 months or longer	551	510
Available for sale, Gross Unrealized Losses 12 months or longer	24	21
Available for sale, Fair Value Total	1,995	2,091
Available for sale, Gross Unrealized Losses Total	58	76
Held to maturity, Fair Value Less than 12 months	595	759
Held to maturity, Gross Unrealized Losses Less than 12 months	11	18
Held to maturity, Fair Value 12 months or longer	407	161
Held to maturity, Gross Unrealized Losses 12 months or longer	14	8
Held to maturity, Fair Value Total	1,002	920
Held to maturity, Gross Unrealized Losses Total	25	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	783	1,039
Available for sale, Gross Unrealized Losses Less than 12 months	13	25
Available for sale, Fair Value 12 months or longer	60	58
Available for sale, Gross Unrealized Losses 12 months or longer	7	9
Available for sale, Fair Value Total	843	1,097
Available for sale, Gross Unrealized Losses Total	$ 20	$ 34