Financial Risk Management Activities (Schedule Of Reconciliation For Derivative Activity Included In Accumulated Other Comprehensive Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) in AOCI	$ 10	$ 13
(Gain) Loss into Income	(2)	4
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	2		4
Pre-Tax Balance at End of Period	(25)		(21)
After-Tax Balance at Beginning of Period	(15)	(1)	(1)
Gain (Loss) in AOCI	(4)	(4)	(17)
(Gain) Loss into Income	1	$ 0	3
After-Tax Balance at End of Period	$ (18)		$ (15)