Investment Securities (Schedule of Marketable Securities) (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	$ 98,770,000,000		$ 99,159,000,000
Available for sale, gross unrealized gains	1,243,000,000		1,162,000,000
Available for sale, gross unrealized losses	851,000,000		1,147,000,000
Available for sale, fair value	99,162,000,000		99,174,000,000
Held to maturity, amortized cost	18,342,000,000		17,740,000,000
Held to maturity, gross unrealized gains	369,000,000		354,000,000
Held to maturity, gross unrealized losses	385,000,000		534,000,000
Held to maturity, fair value	18,326,000,000		17,560,000,000
Total asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	27,609,000,000		29,188,000,000
Available for sale, gross unrealized gains	285,000,000		254,000,000
Available for sale, gross unrealized losses	342,000,000		423,000,000
Available for sale, fair value	27,552,000,000		29,019,000,000
Held to maturity, amortized cost	3,524,000,000		3,171,000,000
Held to maturity, gross unrealized gains	9,000,000		2,000,000
Held to maturity, gross unrealized losses	3,000,000		12,000,000
Held to maturity, fair value	3,530,000,000		3,161,000,000
US Treasury and federal agencies, direct obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1,959,000,000		702,000,000
Available for sale, gross unrealized gains	10,000,000		9,000,000
Available for sale, gross unrealized losses	6,000,000		2,000,000
Available for sale, fair value	1,963,000,000		709,000,000
Held to maturity, amortized cost	5,096,000,000		5,041,000,000
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	328,000,000		448,000,000
Held to maturity, fair value	4,768,000,000		4,593,000,000
US Treasury and federal agencies, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	23,176,000,000		23,744,000,000
Available for sale, gross unrealized gains	206,000,000		211,000,000
Available for sale, gross unrealized losses	290,000,000		392,000,000
Available for sale, fair value	23,092,000,000		23,563,000,000
Held to maturity, amortized cost	81,000,000		91,000,000
Held to maturity, gross unrealized gains	6,000,000		6,000,000
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	87,000,000		97,000,000
Asset-backed securities, student loans
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	14,355,000,000	[1]	14,718,000,000	[1]
Available for sale, gross unrealized gains	128,000,000	[1]	92,000,000	[1]
Available for sale, gross unrealized losses	203,000,000	[1]	268,000,000	[1]
Available for sale, fair value	14,280,000,000	[1]	14,542,000,000	[1]
Held to maturity, amortized cost	1,889,000,000	[1]	1,627,000,000	[1]
Held to maturity, gross unrealized gains	5,000,000	[1]	0	[1]
Held to maturity, gross unrealized losses	2,000,000	[1]	10,000,000	[1]
Held to maturity, fair value	1,892,000,000	[1]	1,617,000,000	[1]
Asset-backed securities, credit cards
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	7,253,000,000		8,230,000,000
Available for sale, gross unrealized gains	21,000,000		21,000,000
Available for sale, gross unrealized losses	37,000,000		41,000,000
Available for sale, fair value	7,237,000,000		8,210,000,000
Held to maturity, amortized cost	897,000,000		762,000,000
Held to maturity, gross unrealized gains	3,000,000		1,000,000
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	900,000,000		763,000,000
Asset-backed securities, sub-prime
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1,234,000,000		1,291,000,000
Available for sale, gross unrealized gains	3,000,000		3,000,000
Available for sale, gross unrealized losses	82,000,000		91,000,000
Available for sale, fair value	1,155,000,000		1,203,000,000
Asset-backed securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,767,000,000		4,949,000,000
Available for sale, gross unrealized gains	133,000,000		138,000,000
Available for sale, gross unrealized losses	20,000,000		23,000,000
Available for sale, fair value	4,880,000,000		5,064,000,000
Held to maturity, amortized cost	738,000,000		782,000,000
Held to maturity, gross unrealized gains	1,000,000		1,000,000
Held to maturity, gross unrealized losses	1,000,000		2,000,000
Held to maturity, fair value	738,000,000		781,000,000
Total non-U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	24,571,000,000		24,615,000,000
Available for sale, gross unrealized gains	313,000,000		314,000,000
Available for sale, gross unrealized losses	18,000,000		22,000,000
Available for sale, fair value	24,866,000,000		24,907,000,000
Held to maturity, amortized cost	6,916,000,000		6,607,000,000
Held to maturity, gross unrealized gains	191,000,000		169,000,000
Held to maturity, gross unrealized losses	29,000,000		48,000,000
Held to maturity, fair value	7,078,000,000		6,728,000,000
Non-U.S. debt securities, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10,978,000,000		10,808,000,000
Available for sale, gross unrealized gains	225,000,000		230,000,000
Available for sale, gross unrealized losses	7,000,000		9,000,000
Available for sale, fair value	11,196,000,000		11,029,000,000
Held to maturity, amortized cost	4,323,000,000		4,211,000,000
Held to maturity, gross unrealized gains	172,000,000		150,000,000
Held to maturity, gross unrealized losses	29,000,000		48,000,000
Held to maturity, fair value	4,466,000,000		4,313,000,000
Non-U.S. debt securities, asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,973,000,000		5,369,000,000
Available for sale, gross unrealized gains	23,000,000		23,000,000
Available for sale, gross unrealized losses	2,000,000		2,000,000
Available for sale, fair value	4,994,000,000		5,390,000,000
Held to maturity, amortized cost	2,399,000,000		2,202,000,000
Held to maturity, gross unrealized gains	19,000,000		19,000,000
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	2,418,000,000		2,221,000,000
Non-US debt securities, government securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,689,000,000		3,759,000,000
Available for sale, gross unrealized gains	3,000,000		2,000,000
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	3,692,000,000		3,761,000,000
Held to maturity, amortized cost	2,000,000		2,000,000
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	2,000,000		2,000,000
Non-U.S. debt securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,931,000,000		4,679,000,000
Available for sale, gross unrealized gains	62,000,000		59,000,000
Available for sale, gross unrealized losses	9,000,000		11,000,000
Available for sale, fair value	4,984,000,000		4,727,000,000
Held to maturity, amortized cost	192,000,000		192,000,000
Held to maturity, gross unrealized gains	0		0
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	192,000,000		192,000,000
State and political subdivisions
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	10,345,000,000		10,301,000,000
Available for sale, gross unrealized gains	216,000,000		160,000,000
Available for sale, gross unrealized losses	117,000,000		198,000,000
Available for sale, fair value	10,444,000,000		10,263,000,000
Held to maturity, amortized cost	16,000,000		24,000,000
Held to maturity, gross unrealized gains	0		1,000,000
Held to maturity, gross unrealized losses	0		0
Held to maturity, fair value	16,000,000		25,000,000
Collateralized mortgage obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	5,253,000,000		5,275,000,000
Available for sale, gross unrealized gains	67,000,000		70,000,000
Available for sale, gross unrealized losses	58,000,000		76,000,000
Available for sale, fair value	5,262,000,000		5,269,000,000
Held to maturity, amortized cost	2,709,000,000		2,806,000,000
Held to maturity, gross unrealized gains	163,000,000		176,000,000
Held to maturity, gross unrealized losses	25,000,000		26,000,000
Held to maturity, fair value	2,847,000,000		2,956,000,000
Other U.S.debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	4,827,000,000		4,876,000,000
Available for sale, gross unrealized gains	139,000,000		138,000,000
Available for sale, gross unrealized losses	20,000,000		34,000,000
Available for sale, fair value	4,946,000,000		4,980,000,000
U.S. equity securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	29,000,000		28,000,000
Available for sale, gross unrealized gains	7,000,000		6,000,000
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	36,000,000		34,000,000
Non-U.S. equity securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1,000,000		1,000,000
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	1,000,000		1,000,000
U.S. money-market mutual funds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	993,000,000		422,000,000
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	993,000,000		422,000,000
Non-U.S. money-market mutual funds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	7,000,000		7,000,000
Available for sale, gross unrealized gains	0		0
Available for sale, gross unrealized losses	0		0
Available for sale, fair value	$ 7,000,000		$ 7,000,000

[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.