Risk Management and Fair Values (Reconciliation Of Changes In The Net Assets (Liabilities) For The Fair Value Of Derivatives Classified As Level 3 In The Fair Value Hierarchy) (Details) (Imported) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Reconciliation of changes in the net assets (liabilities) for the fair value of derivatives classified as Level 3 in the fair value hierarchy
Balance as of Beginning of Period	$ 528	$ 104	$ 312	$ 197
Unrealized gains from price changes	(58)	9	227	(53)
Unrealized gains on originations	6	17	7	15
Realized gains on settlements	(101)	(32)	(171)	(61)
Balance as of End of Period	$ 375	$ 98	$ 375	$ 98