Investment Securities (Schedule of Marketable Securities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	$ 95,834		$ 99,159
Available for sale, gross unrealized gains	1,222		1,162
Available for sale, gross unrealized losses	504		1,147
Available for sale, fair value	96,552		99,174
Held to maturity, amortized cost	18,767		17,740
Held to maturity, gross unrealized gains	353		354
Held to maturity, gross unrealized losses	255		534
Held to maturity, fair value	18,865		17,560
Total asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	21,227		29,188
Available for sale, gross unrealized gains	251		254
Available for sale, gross unrealized losses	221		423
Available for sale, fair value	21,257		29,019
Held to maturity, amortized cost	3,403		3,171
Held to maturity, gross unrealized gains	10		2
Held to maturity, gross unrealized losses	2		12
Held to maturity, fair value	3,411		3,161
US Treasury and federal agencies, direct obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10,751		702
Available for sale, gross unrealized gains	17		9
Available for sale, gross unrealized losses	4		2
Available for sale, fair value	10,764		709
Held to maturity, amortized cost	5,117		5,041
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	222		448
Held to maturity, fair value	4,895		4,593
US Treasury and federal agencies, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	21,203		23,744
Available for sale, gross unrealized gains	196		211
Available for sale, gross unrealized losses	198		392
Available for sale, fair value	21,201		23,563
Held to maturity, amortized cost	68		91
Held to maturity, gross unrealized gains	4		6
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	72		97
Asset-backed securities, student loans
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	12,806		14,718	[1]
Available for sale, gross unrealized gains	122		92	[1]
Available for sale, gross unrealized losses	122		268	[1]
Available for sale, fair value	12,806	[1]	14,542	[1]
Held to maturity, amortized cost	1,873		1,627	[1]
Held to maturity, gross unrealized gains	5		0	[1]
Held to maturity, gross unrealized losses	1		10	[1]
Held to maturity, fair value	1,877	[1]	1,617	[1]
Asset-backed securities, credit cards
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,128		8,230
Available for sale, gross unrealized gains	13		21
Available for sale, gross unrealized losses	30		41
Available for sale, fair value	3,111		8,210
Held to maturity, amortized cost	897		762
Held to maturity, gross unrealized gains	2		1
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	899		763
Asset-backed securities, sub-prime
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1,054		1,291
Available for sale, gross unrealized gains	2		3
Available for sale, gross unrealized losses	59		91
Available for sale, fair value	997		1,203
Asset-backed securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,239		4,949
Available for sale, gross unrealized gains	114		138
Available for sale, gross unrealized losses	10		23
Available for sale, fair value	4,343		5,064
Held to maturity, amortized cost	633		782
Held to maturity, gross unrealized gains	3		1
Held to maturity, gross unrealized losses	1		2
Held to maturity, fair value	635		781
Total non-U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	22,896		24,615
Available for sale, gross unrealized gains	263		314
Available for sale, gross unrealized losses	11		22
Available for sale, fair value	23,148		24,907
Held to maturity, amortized cost	7,631		6,607
Held to maturity, gross unrealized gains	210		169
Held to maturity, gross unrealized losses	16		48
Held to maturity, fair value	7,825		6,728
Non-U.S. debt securities, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10,056		10,808
Available for sale, gross unrealized gains	185		230
Available for sale, gross unrealized losses	2		9
Available for sale, fair value	10,239		11,029
Held to maturity, amortized cost	4,153		4,211
Held to maturity, gross unrealized gains	192		150
Held to maturity, gross unrealized losses	16		48
Held to maturity, fair value	4,329		4,313
Non-U.S. debt securities, asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,433		5,369
Available for sale, gross unrealized gains	15		23
Available for sale, gross unrealized losses	1		2
Available for sale, fair value	3,447		5,390
Held to maturity, amortized cost	3,293		2,202
Held to maturity, gross unrealized gains	18		19
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	3,311		2,221
Non-US debt securities, government securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,605		3,759
Available for sale, gross unrealized gains	8		2
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	3,613		3,761
Held to maturity, amortized cost	110		2
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	110		2
Non-U.S. debt securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	5,802		4,679
Available for sale, gross unrealized gains	55		59
Available for sale, gross unrealized losses	8		11
Available for sale, fair value	5,849		4,727
Held to maturity, amortized cost	75		192
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	75		192
State and political subdivisions
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10,366		10,301
Available for sale, gross unrealized gains	323		160
Available for sale, gross unrealized losses	44		198
Available for sale, fair value	10,645		10,263
Held to maturity, amortized cost	12		24
Held to maturity, gross unrealized gains	0		1
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	12		25
Collateralized mortgage obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,629		5,275
Available for sale, gross unrealized gains	57		70
Available for sale, gross unrealized losses	15		76
Available for sale, fair value	4,671		5,269
Held to maturity, amortized cost	2,536		2,806
Held to maturity, gross unrealized gains	129		176
Held to maturity, gross unrealized losses	15		26
Held to maturity, fair value	2,650		2,956
Other U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,189		4,876
Available for sale, gross unrealized gains	106		138
Available for sale, gross unrealized losses	11		34
Available for sale, fair value	4,284		4,980
U.S. equity securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	29		28
Available for sale, gross unrealized gains	9		6
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	38		34
Non-U.S. equity securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	2		1
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	2		1
U.S. money-market mutual funds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	532		422
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	532		422
Non-U.S. money-market mutual funds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10		7
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	$ 10		$ 7

[1] Substantially composed of securities guaranteed by the federal government with respect to at least 97% of defaulted principal and accrued interest on the underlying loans.