Investment Securities (Schedule of Marketable Securities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	$ 97,739		$ 99,159
Available for sale, gross unrealized gains	1,374		1,162
Available for sale, gross unrealized losses	567		1,147
Available for sale, fair value	98,546		99,174
Held to maturity, amortized cost	18,757		17,740
Held to maturity, gross unrealized gains	386		354
Held to maturity, gross unrealized losses	279		534
Held to maturity, fair value	18,864		17,560
Total asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	26,260		29,188
Available for sale, gross unrealized gains	284		254
Available for sale, gross unrealized losses	280		423
Available for sale, fair value	26,264		29,019
Held to maturity, amortized cost	3,489		3,171
Held to maturity, gross unrealized gains	12		2
Held to maturity, gross unrealized losses	2		12
Held to maturity, fair value	3,499		3,161
US Treasury and federal agencies, direct obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,403		702
Available for sale, gross unrealized gains	33		9
Available for sale, gross unrealized losses	1		2
Available for sale, fair value	3,435		709
Held to maturity, amortized cost	5,119		5,041
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	237		448
Held to maturity, fair value	4,882		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	22,067		23,744
Available for sale, gross unrealized gains	235		211
Available for sale, gross unrealized losses	163		392
Available for sale, fair value	22,139		23,563
Held to maturity, amortized cost	74		91
Held to maturity, gross unrealized gains	5		6
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	79		97
Asset-backed securities, student loans
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	13,985		14,718	[1]
Available for sale, gross unrealized gains	135		92	[1]
Available for sale, gross unrealized losses	158		268	[1]
Available for sale, fair value	13,962	[1]	14,542	[1]
Held to maturity, amortized cost	1,900		1,627	[1]
Held to maturity, gross unrealized gains	6		0	[1]
Held to maturity, gross unrealized losses	1		10	[1]
Held to maturity, fair value	1,905	[1]	1,617	[1]
Asset-backed securities, credit cards
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	6,580		8,230
Available for sale, gross unrealized gains	20		21
Available for sale, gross unrealized losses	34		41
Available for sale, fair value	6,566		8,210
Held to maturity, amortized cost	897		762
Held to maturity, gross unrealized gains	3		1
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	900		763
Asset-backed securities, sub-prime
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1,172		1,291
Available for sale, gross unrealized gains	3		3
Available for sale, gross unrealized losses	74		91
Available for sale, fair value	1,101		1,203
Asset-backed securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,523		4,949
Available for sale, gross unrealized gains	126		138
Available for sale, gross unrealized losses	14		23
Available for sale, fair value	4,635		5,064
Held to maturity, amortized cost	692		782
Held to maturity, gross unrealized gains	3		1
Held to maturity, gross unrealized losses	1		2
Held to maturity, fair value	694		781
Total non-U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	24,930		24,615
Available for sale, gross unrealized gains	297		314
Available for sale, gross unrealized losses	12		22
Available for sale, fair value	25,215		24,907
Held to maturity, amortized cost	7,419		6,607
Held to maturity, gross unrealized gains	218		169
Held to maturity, gross unrealized losses	22		48
Held to maturity, fair value	7,615		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	11,231		10,808
Available for sale, gross unrealized gains	207		230
Available for sale, gross unrealized losses	3		9
Available for sale, fair value	11,435		11,029
Held to maturity, amortized cost	4,274		4,211
Held to maturity, gross unrealized gains	200		150
Held to maturity, gross unrealized losses	21		48
Held to maturity, fair value	4,453		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	4,181		5,369
Available for sale, gross unrealized gains	20		23
Available for sale, gross unrealized losses	1		2
Available for sale, fair value	4,200		5,390
Held to maturity, amortized cost	2,898		2,202
Held to maturity, gross unrealized gains	18		19
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	2,916		2,221
Non-US debt securities, government securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,819		3,759
Available for sale, gross unrealized gains	4		2
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	3,823		3,761
Held to maturity, amortized cost	2		2
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	2		2
Non-U.S. debt securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	5,699		4,679
Available for sale, gross unrealized gains	66		59
Available for sale, gross unrealized losses	8		11
Available for sale, fair value	5,757		4,727
Held to maturity, amortized cost	245		192
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	1		0
Held to maturity, fair value	244		192
State and political subdivisions
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10,400		10,301
Available for sale, gross unrealized gains	289		160
Available for sale, gross unrealized losses	72		198
Available for sale, fair value	10,617		10,263
Held to maturity, amortized cost	15		24
Held to maturity, gross unrealized gains	0		1
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	15		25
Collateralized mortgage obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	5,321		5,275
Available for sale, gross unrealized gains	83		70
Available for sale, gross unrealized losses	30		76
Available for sale, fair value	5,374		5,269
Held to maturity, amortized cost	2,641		2,806
Held to maturity, gross unrealized gains	151		176
Held to maturity, gross unrealized losses	18		26
Held to maturity, fair value	2,774		2,956
Other U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,706		4,876
Available for sale, gross unrealized gains	145		138
Available for sale, gross unrealized losses	9		34
Available for sale, fair value	4,842		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	8		6
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	37		34
Non-U.S. equity securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1		1
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	1		1
U.S. money-market mutual funds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	615		422
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	615		422
Non-U.S. money-market mutual funds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	7		7
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	$ 7		$ 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.