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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) in AOCI	$ 30	$ 8	$ 40	$ 21
(Gain) Loss into Income	(4)	1	(6)	5
Cash Flow Hedges [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pre-Tax Balance at Beginning of Period			(21)	(2)	$ (2)
Gain (Loss) in AOCI			(6)		(23)
(Gain) Loss into Income	4	1	6	1	4
Pre-Tax Balance at End of Period	(21)		(21)		(21)
After-Tax Balance at Beginning of Period			(15)	(1)	(1)
Gain (Loss) in AOCI	0	(13)	(4)	(17)	(17)
(Gain) Loss into Income	3	$ 0	4	$ 0	3
After-Tax Balance at End of Period	$ (15)		$ (15)		$ (15)