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
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (40)	$ 163
Operating Revenues [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(46)	231
Energy Costs [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 6	$ (68)