Employee Postretirement Benefits (Summarized Financial Information about Postretirement plans, Excluding Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Pension Plans
Benefit obligation at beginning of year		$ 3,687	$ 4,296
Service cost		21	36	$ 41
Interest cost		121	128	129
Actuarial (gain) loss(a)	[1]	446	(256)
Currency and other		51	(96)
Benefit payments from plans		(142)	(198)
Direct benefit payments		(10)	(8)
Settlements and curtailments		(127)	(215)
Benefit obligation at end of year		4,047	3,687	4,296
Fair value of plan assets at beginning of year		3,398	3,897
Actual return on plan assets		572	(132)
Employer contributions		50	166
Currency and other		51	(116)
Benefit payments		(142)	(198)
Settlements		(126)	(219)
Fair value of plan assets at end of year		3,803	3,398	3,897
Funded Status		(244)	(289)
Other Postretirement Benefit Plans
Benefit obligation at beginning of year		673	765
Service cost		8	11	12
Interest cost		28	28	32
Actuarial (gain) loss(a)	[1]	36	(79)
Currency and other		0	(5)
Benefit payments from plans		0	0
Direct benefit payments		(52)	(48)
Settlements and curtailments		0	1
Benefit obligation at end of year		693	673	765
Fair value of plan assets at beginning of year		0	0
Actual return on plan assets		0	0
Employer contributions		0	0
Currency and other		0	0
Benefit payments		0	0
Settlements		0	0
Fair value of plan assets at end of year		0	0	$ 0
Funded Status		$ (693)	$ (673)

[1] The actuarial net losses in 2019 and the actuarial net gains in 2018 were primarily due to discount rate decreases in 2019 and discount rate increases in 2018.