Investment Securities (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 security country	Dec. 31, 2011	Dec. 31, 2010
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Aggregate investment securities carried	$ 46,660,000,000	$ 44,660,000,000
Proceeds from sale of securities			11,000,000,000
Pre-tax net loss on sale of securities			344,000,000
Securities sold included as held to maturity		4,800,000,000
Net pre-tax loss on sale of held-to-maturity securities		119,000,000
Impairment associated with expected credit losses	16,000,000	42,000,000	203,000,000
Aggregate pre-tax gross unrealized loss on available for sale securities	882,000,000	1,652,000,000
Number of peripheral european countries	4
Recovery of claimed amounts	20.00%
Net impairment losses	32,000,000	73,000,000	231,000,000
Impairment associated with adverse changes in timing of expected future cash flows	16,000,000	23,000,000	27,000,000
Gross pre-tax unrealized losses on securities	973,000,000
Number of available for sale and held to maturity securities in gross pre-tax unrealized loss position	1,400
European Periphery [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	655,000,000
Aggregate pre-tax gross unrealized loss on available for sale securities	36,000,000
Spain
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	276,000,000
Italy
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	144,000,000
Ireland
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	159,000,000
Portugal
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	76,000,000
Federal Family Education Loan Program [Member]
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 7 months 6 days
Maximum concentration risk on credit instruments	1,000,000,000
Non-US Debt Securities, Mortgage-Backed Securities [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Aggregate pre-tax gross unrealized loss on available for sale securities	27,000,000	107,000,000
Net impairment losses	22,000,000
Non-Agency Prime [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other than temporary impairment recorded in earnings	10,000,000
Impairment associated with expected credit losses	16,000,000	42,000,000
Net impairment losses	32,000,000	73,000,000
Other than temporary impairment losses on investments recognized in earnings		8,000,000
Impairment associated with adverse changes in timing of expected future cash flows	16,000,000	23,000,000
Non-Agency Prime [Member] | European Periphery [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Other than temporary impairment recorded in earnings	6,000,000
Asset-backed Securities [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Aggregate pre-tax gross unrealized loss on available for sale securities	$ 734,000,000	$ 1,297,000,000
Minimum [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Percentage change in additional house price declines	10.00%
Maximum [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Percentage change in additional house price declines	20.00%