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		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) in AOCI	$ 16	$ 30	$ (24)	$ 40
(Gain) Loss into Income	(4)	4	(6)	6
Cash Flow Hedges [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pre-Tax Balance at Beginning of Period			(13)	(21)	$ (21)
Gain (Loss) in AOCI			0		(6)
(Gain) Loss into Income	1	4	2	6	14
Pre-Tax Balance at End of Period	(11)		(11)		(13)
After-Tax Balance at Beginning of Period			(9)	(15)	(15)
Gain (Loss) in AOCI	0	0	0	(4)	(4)
(Gain) Loss into Income	0	$ (3)	(1)	$ (4)	(10)
After-Tax Balance at End of Period	$ (8)		$ (8)		$ (9)