Investment Securities (Schedule of Gross Pre-Tax Unrealized Losses on Investment Securities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	$ 25,178	$ 9,124
Available for sale, Gross Unrealized Losses Less than 12 months	532	56
Available for sale, Fair Value 12 months or longer	12,855	15,885
Available for sale, Gross Unrealized Losses 12 months or longer	525	826
Available for sale, Fair Value Total	38,033	25,009
Available for sale, Gross Unrealized Losses Total	1,057	882
Held to maturity, Fair Value Less than 12 months	9,202	3,968
Held to maturity, Gross Unrealized Losses Less than 12 months	438	10
Held to maturity, Fair Value 12 months or longer	989	1,338
Held to maturity, Gross Unrealized Losses 12 months or longer	66	81
Held to maturity, Fair Value Total	10,191	5,306
Held to maturity, Gross Unrealized Losses Total	504	91
Asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	6,769	2,152
Available for sale, Gross Unrealized Losses Less than 12 months	71	22
Available for sale, Fair Value 12 months or longer	9,125	12,576
Available for sale, Gross Unrealized Losses 12 months or longer	406	712
Available for sale, Fair Value Total	15,894	14,728
Available for sale, Gross Unrealized Losses Total	477	734
Held to maturity, Fair Value Less than 12 months	1,814
Held to maturity, Gross Unrealized Losses Less than 12 months	14
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	1,814
Held to maturity, Gross Unrealized Losses Total	14
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	158	0
Available for sale, Gross Unrealized Losses Less than 12 months	1	0
Available for sale, Fair Value 12 months or longer	117	132
Available for sale, Gross Unrealized Losses 12 months or longer	1	1
Available for sale, Fair Value Total	275	132
Available for sale, Gross Unrealized Losses Total	2	1
Held to maturity, Fair Value Less than 12 months	4,611	3,792
Held to maturity, Gross Unrealized Losses Less than 12 months	390	8
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	4,611	3,792
Held to maturity, Gross Unrealized Losses Total	390	8
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	9,721	3,486
Available for sale, Gross Unrealized Losses Less than 12 months	232	18
Available for sale, Fair Value 12 months or longer	1,933	865
Available for sale, Gross Unrealized Losses 12 months or longer	30	8
Available for sale, Fair Value Total	11,654	4,351
Available for sale, Gross Unrealized Losses Total	262	26
Asset-backed securities, student loans
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	2,123	625
Available for sale, Gross Unrealized Losses Less than 12 months	19	6
Available for sale, Fair Value 12 months or longer	7,463	10,241
Available for sale, Gross Unrealized Losses 12 months or longer	283	502
Available for sale, Fair Value Total	9,586	10,866
Available for sale, Gross Unrealized Losses Total	302	508
Held to maturity, Fair Value Less than 12 months	1,234
Held to maturity, Gross Unrealized Losses Less than 12 months	11
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	1,234
Held to maturity, Gross Unrealized Losses Total	11
Asset-backed securities, credit cards
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	3,734	888
Available for sale, Gross Unrealized Losses Less than 12 months	46	3
Available for sale, Fair Value 12 months or longer	0	0
Available for sale, Gross Unrealized Losses 12 months or longer	0	0
Available for sale, Fair Value Total	3,734	888
Available for sale, Gross Unrealized Losses Total	46	3
Asset-backed securities, sub-prime
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	16	0
Available for sale, Gross Unrealized Losses Less than 12 months	1	0
Available for sale, Fair Value 12 months or longer	1,193	1,346
Available for sale, Gross Unrealized Losses 12 months or longer	109	162
Available for sale, Fair Value Total	1,209	1,346
Available for sale, Gross Unrealized Losses Total	110	162
Asset-backed securities, other
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	896	639
Available for sale, Gross Unrealized Losses Less than 12 months	5	13
Available for sale, Fair Value 12 months or longer	469	989
Available for sale, Gross Unrealized Losses 12 months or longer	14	48
Available for sale, Fair Value Total	1,365	1,628
Available for sale, Gross Unrealized Losses Total	19	61
Held to maturity, Fair Value Less than 12 months	580
Held to maturity, Gross Unrealized Losses Less than 12 months	3
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	580
Held to maturity, Gross Unrealized Losses Total	3
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	3,382	2,152
Available for sale, Gross Unrealized Losses Less than 12 months	18	5
Available for sale, Fair Value 12 months or longer	263	506
Available for sale, Gross Unrealized Losses 12 months or longer	12	27
Available for sale, Fair Value Total	3,645	2,658
Available for sale, Gross Unrealized Losses Total	30	32
Held to maturity, Fair Value Less than 12 months	1,872	56
Held to maturity, Gross Unrealized Losses Less than 12 months	7	1
Held to maturity, Fair Value 12 months or longer	893	1,185
Held to maturity, Gross Unrealized Losses 12 months or longer	62	70
Held to maturity, Fair Value Total	2,765	1,241
Held to maturity, Gross Unrealized Losses Total	69	71
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	1,240	670
Available for sale, Gross Unrealized Losses Less than 12 months	3	3
Available for sale, Fair Value 12 months or longer	242	453
Available for sale, Gross Unrealized Losses 12 months or longer	10	24
Available for sale, Fair Value Total	1,482	1,123
Available for sale, Gross Unrealized Losses Total	13	27
Held to maturity, Fair Value Less than 12 months	1,155	56
Held to maturity, Gross Unrealized Losses Less than 12 months	5	1
Held to maturity, Fair Value 12 months or longer	893	956
Held to maturity, Gross Unrealized Losses 12 months or longer	62	67
Held to maturity, Fair Value Total	2,048	1,012
Held to maturity, Gross Unrealized Losses Total	67	68
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	708	973
Available for sale, Gross Unrealized Losses Less than 12 months	1	1
Available for sale, Fair Value 12 months or longer	21	53
Available for sale, Gross Unrealized Losses 12 months or longer	2	3
Available for sale, Fair Value Total	729	1,026
Available for sale, Gross Unrealized Losses Total	3	4
Held to maturity, Fair Value Less than 12 months	717	0
Held to maturity, Gross Unrealized Losses Less than 12 months	2	0
Held to maturity, Fair Value 12 months or longer	0	73
Held to maturity, Gross Unrealized Losses 12 months or longer	0	1
Held to maturity, Fair Value Total	717	73
Held to maturity, Gross Unrealized Losses Total	2	1
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	1,434	509
Available for sale, Gross Unrealized Losses Less than 12 months	14	1
Available for sale, Fair Value 12 months or longer	0	0
Available for sale, Gross Unrealized Losses 12 months or longer	0	0
Available for sale, Fair Value Total	1,434	509
Available for sale, Gross Unrealized Losses Total	14	1
Held to maturity, Fair Value Less than 12 months		0
Held to maturity, Gross Unrealized Losses Less than 12 months		0
Held to maturity, Fair Value 12 months or longer		156
Held to maturity, Gross Unrealized Losses 12 months or longer		2
Held to maturity, Fair Value Total		156
Held to maturity, Gross Unrealized Losses Total		2
State and political subdivisions
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	2,436	685
Available for sale, Gross Unrealized Losses Less than 12 months	118	9
Available for sale, Fair Value 12 months or longer	1,080	1,152
Available for sale, Gross Unrealized Losses 12 months or longer	62	58
Available for sale, Fair Value Total	3,516	1,837
Available for sale, Gross Unrealized Losses Total	180	67
Collateralized mortgage obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	1,665	347
Available for sale, Gross Unrealized Losses Less than 12 months	65	1
Available for sale, Fair Value 12 months or longer	304	621
Available for sale, Gross Unrealized Losses 12 months or longer	8	14
Available for sale, Fair Value Total	1,969	968
Available for sale, Gross Unrealized Losses Total	73	15
Held to maturity, Fair Value Less than 12 months	905	120
Held to maturity, Gross Unrealized Losses Less than 12 months	27	1
Held to maturity, Fair Value 12 months or longer	96	153
Held to maturity, Gross Unrealized Losses 12 months or longer	4	11
Held to maturity, Fair Value Total	1,001	273
Held to maturity, Gross Unrealized Losses Total	31	12
Other U.S.debt securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, Fair Value Less than 12 months	1,047	302
Available for sale, Gross Unrealized Losses Less than 12 months	27	1
Available for sale, Fair Value 12 months or longer	33	33
Available for sale, Gross Unrealized Losses 12 months or longer	6	6
Available for sale, Fair Value Total	1,080	335
Available for sale, Gross Unrealized Losses Total	$ 33	$ 7