Derivative Financial Instruments (Narrative) (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
Derivative transactions entered into	$ 1,443	$ 447	$ 2,047	$ 779
Derivative transactions terminated	$ 1,523	$ 391	$ 2,065	$ 712