Investment Securities (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013 country		Sep. 30, 2012	Sep. 30, 2013 security country		Sep. 30, 2012	Dec. 31, 2012
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	$ 10,000,000		$ 6,000,000	$ 20,000,000		$ 27,000,000
Impairment associated with adverse changes in timing of expected future cash flows	2,000,000		5,000,000	6,000,000		13,000,000
Impairment associated with management's intent to sell impaired securities prior to recovery in value	0		0	6,000,000		0
Impairment associated with expected credit losses	(8,000,000)		(1,000,000)	(8,000,000)		(14,000,000)
Available for sale, gross unrealized gains	1,292,000,000			1,292,000,000			2,001,000,000
Available for sale, gross unrealized losses	(1,057,000,000)			(1,057,000,000)			(882,000,000)
Number of peripheral european countries	4			4
Gross pre-tax unrealized losses on securities				(1,560,000,000)
Number of available for sale and held to maturity securities in gross pre-tax unrealized loss position				2,607
Pledged Financial Instruments, Not Separately Reported, Securities	48,280,000,000			48,280,000,000			46,660,000,000
U.S. agency residential mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	0		0	0		0
Non-U.S. debt securities, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	2,000,000		5,000,000	6,000,000		19,000,000
Impairment associated with adverse changes in timing of expected future cash flows						13,000,000
Available for sale, gross unrealized gains	241,000,000			241,000,000			313,000,000
Available for sale, gross unrealized losses	(13,000,000)			(13,000,000)			(27,000,000)
Non-U.S. debt securities, mortgage-backed securities | European Periphery
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	0		0	6,000,000		6,000,000
Total exposure to asset backed securities	570,000,000			570,000,000
Aggregate pre-tax gross unrealized gain (loss) on available for sale securities	39,000,000			39,000,000
Available for sale, gross unrealized gains	63,000,000			63,000,000
Available for sale, gross unrealized losses	(24,000,000)			(24,000,000)
Non-U.S. debt securities, mortgage-backed securities | Spain
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed securities	269,000,000			269,000,000
Non-U.S. debt securities, mortgage-backed securities | Italy
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed securities	106,000,000			106,000,000
Non-U.S. debt securities, mortgage-backed securities | Ireland
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed securities	118,000,000			118,000,000
Non-U.S. debt securities, mortgage-backed securities | Portugal
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed securities	77,000,000			77,000,000
Asset-backed securities, student loans
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	0		0	0		0
Available for sale, gross unrealized gains	94,000,000	[1]		94,000,000	[1]		100,000,000	[1]
Available for sale, gross unrealized losses	(302,000,000)	[1]		(302,000,000)	[1]		(508,000,000)	[1]
Federal Family Education Loan Program
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Federal government credit support guarantee, percentage minimum				97.00%
Collective credit support, percentage minimum				100.00%
Average remaining term of FFELP loan-backed securities				5 years
Maximum concentration risk on credit instruments (less than)				900,000,000
Direct sovereign debt
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed securities	0			0
State and political subdivisions
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded			0	0		0
Available for sale, gross unrealized gains	171,000,000			171,000,000			234,000,000
Available for sale, gross unrealized losses	(180,000,000)			(180,000,000)			(67,000,000)
U.S. non-agency residential mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	0		1,000,000	0		8,000,000
Collateralized mortgage obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other-than-temporary impairment recorded	8,000,000			8,000,000
Available for sale, gross unrealized gains	79,000,000			79,000,000			151,000,000
Available for sale, gross unrealized losses	$ (73,000,000)			$ (73,000,000)			$ (15,000,000)
Minimum
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Percentage change in additional house price declines				10.00%
Maximum
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Percentage change in additional house price declines				18.00%

[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.