Retirement Benefits Funded Status of Plan Assets (Liabilities) (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in plan assets
Fair value of plan assets at beginning of year	$ 30,146
Fair value of plan assets at end of year	31,525	$ 30,146
Change in projected benefit obligation
Interest cost	1,600
Benefits paid	(2,100)
Amounts Recognized on the Balance Sheet
Non-current liability	(1,290)	(1,188)
Pension Benefits
Change in plan assets
Fair value of plan assets at beginning of year	28,920	36,236
Net gain (loss) on plan assets	3,104	(5,422)
Employer contributions	105	101
Participant contributions	6	7
Benefits paid	1,894	1,973
Other	10	(29)
Fair value of plan assets at end of year	30,251	28,920	$ 36,236
Change in projected benefit obligation
Projected benefit obligation at beginning of year	29,067	38,888
Service cost	236	367	414
Interest cost	1,568	1,136	1,054
Participant contributions	6	7
Actuarial loss (gain)	1,447	(9,325)
Benefits paid	1,894	1,973
Other	13	(33)
Projected benefit obligation at end of year	30,443	29,067	38,888
Funded status	(192)	(147)
Amounts Recognized on the Balance Sheet
Non-current assets	1,042	982
Current liability	(178)	(177)
Non-current liability	(1,056)	(952)
Medical and Life Benefits
Change in plan assets
Fair value of plan assets at beginning of year	1,226	1,588
Net gain (loss) on plan assets	146	(257)
Employer contributions	34	35
Participant contributions	27	24
Benefits paid	159	164
Other	0	0
Fair value of plan assets at end of year	1,274	1,226	1,588
Change in projected benefit obligation
Projected benefit obligation at beginning of year	1,264	1,685
Service cost	5	9	16
Interest cost	67	47	53
Participant contributions	27	24
Actuarial loss (gain)	42	(337)
Benefits paid	159	164
Other	0	0
Projected benefit obligation at end of year	1,246	1,264	$ 1,685
Funded status	28	(38)
Amounts Recognized on the Balance Sheet
Non-current assets	289	240
Current liability	(27)	(42)
Non-current liability	$ (234)	$ (236)