Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (76)	$ (64)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	21	23
Interest cost	55	55
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(82)	(83)
Prior service benefit	0	0
Actuarial (gain)	(17)	(29)
Total non-service cost components	(44)	(57)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (23)	(34)
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	$ 3	3
Interest cost	11	11
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(23)	(23)
Prior service benefit	(1)	(1)
Actuarial (gain)	(10)	(11)
Total non-service cost components	(23)	(24)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (20)	$ (21)
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