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, 2024	Mar. 31, 2023	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Gain) Loss Reclassified into Income, pre-tax	$ 4	$ 16
Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss), Net of Tax	8	18
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	2	10
Cash Flow Hedges [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pre-Tax Balance at Beginning of Period	4	(4)	$ (4)
Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss), pre-tax	28		13
(Gain) Loss Reclassified into Income, pre-tax	(3)		(5)
Pre-Tax Balance at End of Period	29		4
After-Tax Balance at Beginning of Period	3	(3)	(3)
Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss), Net of Tax	20	(2)	9
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(2)	$ 1	(3)
After-Tax Balance at End of Period	$ 21		$ 3