Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (64)	$ (46)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	23	33
Interest cost	55	40
Expected return on plan assets(b)	(83)	(80)
Prior service benefit	0	0
Actuarial loss (gain)	(29)	6
Total non-service cost components	(57)	(34)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (34)	(1)
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	5
Interest cost	11	8
Expected return on plan assets(b)	(23)	(21)
Prior service benefit	(1)	(1)
Actuarial loss (gain)	(11)	(4)
Total non-service cost components	(24)	(18)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (21)	$ (13)
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