Preferred Stock Preferred Stock Summary (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Class of Stock [Line Items]
Carrying value	$ 1,068		$ 1,068
Series A Noncumulative Perpetual Preferred Stock
Class of Stock [Line Items]
Total shares issued and outstanding (shares)	5,001		5,001
Liquidation preference per share (usd per share)	$ 100,000
Carrying value	500	[1]	500	[1]
Per annum dividend rate	Greater of (i) three- month LIBOR plus 0.565% for the related distribution period; or (ii) 4.000%
Dividends paid per share (usd per share)	$ 1,000		$ 1,011
Series C Noncumulative Perpetual Preferred Stock
Class of Stock [Line Items]
Total shares issued and outstanding (shares)	5,825		5,825
Liquidation preference per share (usd per share)	$ 100,000
Carrying value	$ 568	[1]	$ 568	[1]
Per annum dividend rate (percent)	5.20%
Dividends paid per share (usd per share)	$ 1,300		$ 1,314

[1] The carrying value of the Series C preferred stock is recorded net of issuance costs.