Retirement Programs - Schedule of Pension and OPEB Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amount recognized in Net pension and OPEB cost (benefit), excluding service cost
Settlement charge	$ 4	$ 6
Net pension and OPEB cost (benefit)	(45)	(41)	$ (143)	$ (131)
After-tax pension settlement charges	3	5
Pensions
Amount recognized in Operating Profit
Service cost	39	38	117	111
Amount recognized in Net pension and OPEB cost (benefit), excluding service cost
Interest cost	39	52	115	154
Expected return on plan assets	(129)	(122)	(391)	(360)
Net amortization and deferral	41	22	130	67
Settlement charge	4	6	4	6
Net pension and OPEB cost (benefit)	(45)	(42)	(142)	(133)
Net periodic benefit cost (benefit)	(6)	(4)	(25)	(22)
OPEB
Amount recognized in Operating Profit
Service cost	0	1	1	2
Amount recognized in Net pension and OPEB cost (benefit), excluding service cost
Interest cost	2	1	3	4
Expected return on plan assets	0	0	0	0
Net amortization and deferral	(2)		(4)	(2)
Settlement charge	0	0	0	0
Net pension and OPEB cost (benefit)	0	1	(1)	2
Net periodic benefit cost (benefit)	$ 0	$ 2	$ 0	$ 4