Debt Repurchases and Calls (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Debt Repurchases and Calls [Line Items]
Gains/(Losses) on extinguishment of debt	$ (1)	$ (6)	$ (1)	$ (9)
Unsecured Debt [Member]
Debt Repurchases and Calls [Line Items]
Extinguishment of debt amount	130		163
Gains/(Losses) on extinguishment of debt	(1)		(1)
Unsecured and Asset Backed Debt [Member]
Debt Repurchases and Calls [Line Items]
Extinguishment of debt amount		165		215
Amount of debt extinguished that was due to mature in the current year		37		37
Gains/(Losses) on extinguishment of debt		$ (6)		$ (9)