Investment Securities (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 country	Jun. 30, 2012	Jun. 30, 2013 security country	Jun. 30, 2012	Dec. 31, 2012
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Aggregate investment securities carried	$ 46,970,000,000		$ 46,970,000,000		$ 46,660,000,000
Impairment associated with expected credit losses	0	9,000,000	0	13,000,000
Net impairment losses	7,000,000	13,000,000	10,000,000	21,000,000
Impairment associated with management's intent to sell the impaired securities prior to their recovery in value	6,000,000	0	6,000,000	0
Impairment associated with adverse changes in timing of expected future cash flows	1,000,000	4,000,000	4,000,000	8,000,000
Available for sale, gross unrealized gains	1,308,000,000		1,308,000,000		2,001,000,000
Available for sale, gross unrealized losses	(1,193,000,000)		(1,193,000,000)		(882,000,000)
Number of peripheral european countries	4		4
Gross pre-tax unrealized losses on securities			(1,630,000,000)
Number of available for sale and held to maturity securities in gross pre-tax unrealized loss position			2,738
European Periphery
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	556,000,000		556,000,000
Aggregate pre-tax gross unrealized gain (loss) on available for sale securities	33,000,000		33,000,000
Available for sale, gross unrealized gains	58,000,000		58,000,000
Available for sale, gross unrealized losses	(25,000,000)		(25,000,000)
Spain
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	261,000,000		261,000,000
Italy
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	106,000,000		106,000,000
Ireland
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	114,000,000		114,000,000
Portugal
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Total exposure to asset backed Securities	75,000,000		75,000,000
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 1 month 6 days
Maximum concentration risk on credit instruments (less than)			900,000,000
Non-U.S. debt securities, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Net impairment losses	1,000,000		4,000,000
Impairment associated with management's intent to sell the impaired securities prior to their recovery in value		10,000,000		14,000,000
Impairment associated with adverse changes in timing of expected future cash flows		4,000,000		8,000,000
Available for sale, gross unrealized gains	251,000,000		251,000,000		313,000,000
Available for sale, gross unrealized losses	(13,000,000)		(13,000,000)		(27,000,000)
Other than temporary impairment due to credit losses on securities		6,000,000		6,000,000
Non-Agency Prime [Member]
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Impairment associated with expected credit losses	0	3,000,000	0	7,000,000
Impairment associated with management's intent to sell the impaired securities prior to their recovery in value			$ 6,000,000
Minimum
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Percentage change in additional house price declines			9.00%
Maximum
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Percentage change in additional house price declines			18.00%