Retirement Programs - Schedule of Pension and OPEB Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Curtailment and termination benefits		$ (7)
Net pension and OPEB cost (benefit)	$ (45)	(24)		$ (90)	$ (9)
Termination charge		17
Benefits paid			$ 91
Pensions
Defined Benefit Plan Disclosure [Line Items]
Service cost	36	39		73	78
Interest cost	50	65		102	133
Expected return on plan assets	(118)	(113)		(238)	(232)
Net amortization and deferral	22	14		45	28
Curtailment and termination benefits	0	10		0	10
Settlement charge	0	0	51	0	51
Net pension and OPEB cost (benefit)	(46)	(24)		(91)	(10)
Net periodic benefit cost	(10)	15		(18)	68
After-tax pension settlement charges			$ 38
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0		1	1
Interest cost	2	1		3	3
Expected return on plan assets	0	0		0	0
Net amortization and deferral	(1)	(1)		(2)	(2)
Curtailment and termination benefits	0	0		0	0
Settlement charge	0	0		0	0
Net pension and OPEB cost (benefit)	1	0		1	1
Net periodic benefit cost	$ 1	$ 0		$ 2	$ 2