Significant Accounting Policies Significant Accounting Policies - additional information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Noninterest Expense	$ 137	[1]	$ 105	[1]
provision for income taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Depreciation and Amortization	$ 13		$ 10

[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.