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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (781)	$ (34)	$ (1,119)	$ 104
Operating Revenues [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(897)	(49)	(1,316)	155
Energy Costs [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 116	$ 15	$ 197	$ (51)