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	6 Months Ended
	Sep. 30, 2013	Jun. 30, 2013
Pre-Tax Balance at Beginning of Period	$ 5	$ 12
Gain (Loss) in AOCI	1
Less: Gain Reclassified into Income	(3)	(7)
Pre-Tax Balance at End of Period	3	5
After-Tax Balance at Beginning of Period	3	7
Gain (Loss) in AOCI, After-Tax	1
Less: Gain Reclassified into Income, After-Tax	(2)	(4)
After-Tax Balance at End of Period	$ 2	$ 3