Financial Risk Management Activities (Schedule Of Derivative Instruments Designated As Cash Flow Hedges) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pre-Tax Gain (Loss) attributed to Cash Flow Hedges Recognized in AOCI on Derivatives (Effective Portion)	$ 0	$ (6)	$ (23)
Amount of Pre-Tax Loss Reclassified from AOCL into Income, Effective Portion	(4)	(14)	(4)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	11	(4)	7
Interest Expense [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pre-Tax Gain (Loss) attributed to Cash Flow Hedges Recognized in AOCI on Derivatives (Effective Portion)	0	(6)	(23)
Amount of Pre-Tax Loss Reclassified from AOCL into Income, Effective Portion	(4)	(14)	(4)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	$ 3	$ 10	$ 3