Financial Risk Management Activities (Schedule Of Reconciliation For Derivative Activity Included In Accumulated Other Comprehensive Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Mar. 31, 2012
Balance as of December 31, 2011	$ 53	$ 54
Loss Recognized in AOCI, After-Tax	(5)
Gain (Loss) Recognized in AOCI	(8)	34
Less: Gain Reclassified into Income	(7)	(35)
Balance as of June 30, 2012	38	53
Balance as of December 31, 2011	31	31
Gain Recognized in AOCI, After-Tax		20
Less: Gain Reclassified into Income, After-Tax	(5)	(20)
Balance as of June 30, 2012	$ 21	$ 31