Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (66)	$ (76)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	21	21
Interest cost	58	55
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(76)	(82)
Prior service cost (credit)	0	0
Actuarial (gain)	(10)	(17)
Total non-service cost components	(28)	(44)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (7)	(23)
Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss)	10 years
Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period	4 years
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 2	3
Interest cost	11	11
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(23)	(23)
Prior service cost (credit)	(1)	(1)
Actuarial (gain)	(9)	(10)
Total non-service cost components	(22)	(23)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (20)	$ (20)
Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss)	10 years
Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period	4 years