Financial Risk Management Activities (Schedule Of Derivative Transactions Designated And Effective As Cash Flow Hedges) (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]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 28	$ (3)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion		(1)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(2)	(10)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	3
Cash Flow Hedges [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2	(1)	$ 3
Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	28	(3)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion		$ (1)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 3