Financial Risk Management Activities (Schedule Of Reconciliation For Derivative Activity Included In Accumulated Other Comprehensive Loss) (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) in AOCI	$ (14)		$ 24	$ 3	$ 30
(Gain) Loss into Income	7		(10)	3	(8)
Cash Flow Hedges [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pre-Tax Balance at Beginning of Period	1	$ 17		17
Gain (Loss) in AOCI	0	1
(Gain) Loss into Income	0	(17)	0	(17)	12
Pre-Tax Balance at End of Period	1	1		1
After-Tax Balance at Beginning of Period	1	10		10
Gain (Loss) in AOCI	0	1	1	1	(4)
(Gain) Loss into Income	0	(10)	$ 0	(10)	$ 7
After-Tax Balance at End of Period	$ 1	$ 1		$ 1