Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Amortization of:
Non-service net periodic benefit cost	$ 16	$ 19	$ 48	$ 64
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	58	74	177	222
Interest cost	110	102	330	304
Expected return on assets	(205)	(212)	(619)	(633)
Amortization of:
Prior service cost (credit)	1	1	3	3
Actuarial loss	73	100	222	299
Curtailment benefits			0	0
Settlement charges	0	2	0	2
Non-service net periodic benefit cost	37	67	113	197
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	13	30	38
Interest cost	19	18	57	52
Expected return on assets	(25)	(26)	(75)	(75)
Amortization of:
Prior service cost (credit)	(5)	(6)	(15)	(18)
Actuarial loss	4	7	12	19
Curtailment benefits			0	(1)
Settlement charges	0	0	0	0
Non-service net periodic benefit cost	$ 3	$ 6	$ 9	$ 15