Financial Instruments (Free-standing derivatives) (Details) (Free Standing Derivatives [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Free standing derivatives
Gain (loss) on derivatives	$ (608)	$ (667)
Interest Rate Contract [Member]
Free standing derivatives
Gain (loss) on derivatives	(291)	(25)
Foreign Exchange Contract [Member]
Free standing derivatives
Gain (loss) on derivatives	(310)	(666)
Other Contract [Member]
Free standing derivatives
Gain (loss) on derivatives	$ (7)	$ 24