Debt Repurchases and Calls (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Repurchases and Calls [Line Items]
Loss on extinguishment of debt	$ (14)	$ (66)	$ (139)
Unsecured Debt [Member]
Debt Repurchases and Calls [Line Items]
Extinguishment of debt amount		2,300
Amount of debt extinguished that was due to mature in the current year		266
Loss on extinguishment of debt		(66)
Unsecured and Asset Backed Debt [Member]
Debt Repurchases and Calls [Line Items]
Extinguishment of debt amount	628		5,600
Amount of debt extinguished that was due to mature in the current year	43		683
Loss on extinguishment of debt	$ (14)		$ (139)