Investment Securities (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012 securities	Mar. 31, 2011	Dec. 31, 2011
Aggregate investment securities carried	$ 38,270,000,000		$ 44,660,000,000
Unrealized loss on available-for-sale securities	1,494,000,000		1,652,000,000
OTTI on Spanish Italian Irish Portugese Mortgage and Asset Backed Securities	0
Number Of Peripheral European Countries	5
Recovery of claimed amounts	20.00%
Net impairment losses	8,000,000	11,000,000
Gross pre-tax unrealized losses on securities	1,710,000,000
Number of investment securities	1,900
Non-Agency Prime [Member]
Credit-related other-than-temporary impairment	4,000,000	5,000,000
Losses From Adverse Changes in Timing of Expected Future Cash Flows, Other Than Temporary Impairment	4,000,000	6,000,000
Net impairment losses	8,000,000	11,000,000
Federal Family Education Loan Program [Member]
Federal government credit support guarantee, percentage minimum	97.00%
Collective credit support, percentage minimum	100.00%
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	1,000,000,000
European Periphery [Member]
Total exposure to asset backed Securities	1,090,000,000
Unrealized loss on available-for-sale securities	100,000,000
Spain
Total exposure to asset backed Securities	435,000,000
Italy
Total exposure to asset backed Securities	371,000,000
Greece
Total exposure to asset backed Securities	98,000,000
Ireland
Total exposure to asset backed Securities	115,000,000
Portugal
Total exposure to asset backed Securities	$ 75,000,000
Minimum [Member]
Percentage change in additional house price declines	4.00%
Maximum [Member]
Percentage change in additional house price declines	14.00%