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, 2013	Mar. 31, 2013
Pre-Tax Balance at Beginning of Period	$ 6	$ 12
Less: Gain Reclassified into Income	(1)	(6)
Pre-Tax Balance at End of Period	5	6
After-Tax Balance at Beginning of Period	3	7
Less: Gain Reclassified into Income, After-Tax	0	(4)
After-Tax Balance at End of Period	$ 3	$ 3