Benefit Plans (Amounts Recorded in Accumulated Other Comprehensive Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (loss) gain	$ (2,256)	$ (2,213)
Prior service (cost) credit	233	264
Deferred income taxes	530	513
Amounts recorded in accumulated other comprehensive losses	(1,493)	(1,436)
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (loss) gain	(2,236)	(2,180)
Prior service (cost) credit	(18)	(24)
Deferred income taxes	585	571
Amounts recorded in accumulated other comprehensive losses	(1,669)	(1,633)
Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (loss) gain	19	1
Prior service (cost) credit	256	293
Deferred income taxes	(67)	(68)
Amounts recorded in accumulated other comprehensive losses	208	226
Postemployment Retirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (loss) gain	(39)	(34)
Prior service (cost) credit	(5)	(5)
Deferred income taxes	12	10
Amounts recorded in accumulated other comprehensive losses	$ (32)	$ (29)