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, 2014	Mar. 31, 2013	Dec. 31, 2013
Gain (Loss) in AOCI	$ 6	$ 27
(Gain) Loss into Income	2	6
Cash Flow Hedges [Member]
Pre-Tax Balance at Beginning of Period	(4)	12	12
Gain (Loss) in AOCI	(8)		(4)
(Gain) Loss into Income	12	(6)	(12)
Pre-Tax Balance at End of Period	0		(4)
After-Tax Balance at Beginning of Period	(2)	7	7
Gain (Loss) in AOCI	(5)	0	(2)
(Gain) Loss into Income	7	(4)	(7)
After-Tax Balance at End of Period	$ 0		$ (2)