Financial Risk Management Activities (Schedule Of Reconciliation For Derivative Activity Included In Accumulated Other Comprehensive Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Gain (Loss) Recognized in AOCI, After-Tax	$ 135	$ (299)
Less: Gain Reclassified to Income, After-Tax	53	6
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of Beginning of Year	(4)	12
Gain (Loss) Recognized in AOCI, Pre-Tax	12	(4)
Less: Gain Reclassified into Income, Pre-Tax	9	(12)
Balance as of End of Year	17	(4)
Balance as of Beginning of Year	(2)	7
Gain (Loss) Recognized in AOCI, After-Tax	(7)	2
Less: Gain Reclassified to Income, After-Tax	(5)	7
Balance as of End of Year	$ 10	$ (2)