Financial Risk Management Activities (Schedule Of Derivative Instruments Not Designated As Hedging Instruments And Impact On Results Of Operations) (Detail) - Energy-Related Contracts [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (25)	$ 261	$ 138	$ 387
Operating Revenues [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(27)	322	204	461
Energy Costs [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 2	$ (61)	$ (66)	$ (74)