Significant Accounting Policies Significant Accounting Policies - additional information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Noninterest Expense	$ 133	[1]	$ 129	[1]	$ 277	[1]	$ 249	[1]
provision for income taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Depreciation and Amortization	14		10
provision for income taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Depreciation and Amortization	$ 14		$ 10		$ 27		$ 20

[1] Amortization expense related to qualified affordable housing investment costs is recognized in provision 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.