Income Taxes - Additional Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Income Taxes Other Information [Line Items]
Income Tax Expense (Benefit)	$ 67	[1]	$ (133)	[1]	$ 364	[1]	$ 184	[1]
Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority	130				130
Effective Income Tax Rate Reconciliation, Percent	10.40%				20.90%		16.70%
Unrecognized Tax Benefits	158				158				291
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 50				$ 50

[1] Amortization expense related to qualified affordable housing investment costs is recognized in provision/(benefit) for income taxes for each of the periods presented as allowed by a recently adopted accounting standard. Prior to the first quarter of 2014, these amounts were recognized in other noninterest expense.