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		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Gain (Loss) in AOCI	$ 17	$ 6
(Gain) Loss into Income	(4)	2
Cash Flow Hedges [Member]
Pre-Tax Balance at Beginning of Period	17	(4)	(4)
Gain (Loss) in AOCI	1		12
(Gain) Loss into Income	(17)	12	9
Pre-Tax Balance at End of Period	1		17
After-Tax Balance at Beginning of Period	10	(2)	(2)
Gain (Loss) in AOCI	1	(5)	7
(Gain) Loss into Income	(10)	7	5
After-Tax Balance at End of Period	$ 1		$ 10