Retirement Programs - Schedule of Pension and OPEB Net Periodic Benefit Costs (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net pension and OPEB cost (benefit)	$ (45)	$ 15
Benefits paid		91
Pensions
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	39
Interest cost	52	68
Expected return on plan assets	(120)	(119)
Net amortization and deferral	23	14
Settlement charge	0	51
Net pension and OPEB cost (benefit)	(45)	14
Net periodic benefit cost	(8)	53
After-tax pension settlement charges		$ 38
Settlement charges per diluted share (in dollars per share)		$ 0.07
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	$ 1
Interest cost	1	2
Expected return on plan assets	0	0
Net amortization and deferral	(1)	(1)
Settlement charge	0	0
Net pension and OPEB cost (benefit)	0	1
Net periodic benefit cost	$ 1	$ 2