Postretirement Benefit Plans - Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in plan assets
Funded status at end of year	$ 104	$ (37)
U.S. | Defined benefit plan
Change in plan benefit obligation
Benefit obligation at beginning of year	874	998
Service cost	18	19	$ 22
Interest cost	38	35	42
Participant contributions	0	0
Benefits paid	(11)	(10)
Settlements	(66)	(100)
Curtailments	0	0
Actuarial loss (gain)	107	(68)
Plan amendments	0	0
Effects of exchange rate changes	0	0
Benefit obligation at end of year	960	874	998
Change in plan assets
Fair value of plan assets at beginning of year	869	995
Actual return on plan assets	185	(56)
Employer contributions (qualified plans)	0	20
Employer contributions (non-qualified plans)	10	20
Participant contributions	0	0
Benefits paid	(11)	(10)
Settlements	(66)	(100)
Effects of exchange rate changes	0	0
Other	0	0
Fair value of plan assets at end of year	987	869	995
Funded status at end of year	27	(5)
U.S. | Retiree health care plan
Change in plan benefit obligation
Benefit obligation at beginning of year	361	414
Service cost	3	5
Interest cost	14	15
Participant contributions	13	11
Benefits paid	(41)	(41)
Settlements	0	0
Curtailments	0	0
Actuarial loss (gain)	9	(43)
Plan amendments	0	0
Effects of exchange rate changes	0	0
Benefit obligation at end of year	359	361	414
Change in plan assets
Fair value of plan assets at beginning of year	330	394
Actual return on plan assets	53	(12)
Employer contributions (qualified plans)	1	1
Employer contributions (non-qualified plans)	0	0
Participant contributions	13	11
Benefits paid	(41)	(41)
Settlements	0	0
Effects of exchange rate changes	0	0
Other	0	(23)
Fair value of plan assets at end of year	356	330	394
Funded status at end of year	(3)	(31)
Non-U.S. | Defined benefit plan
Change in plan benefit obligation
Benefit obligation at beginning of year	2,411	2,469
Service cost	31	36	37
Interest cost	43	45	44
Participant contributions	7	7
Benefits paid	(103)	(87)
Settlements	(12)	(16)
Curtailments	(1)	0
Actuarial loss (gain)	193	6
Plan amendments	0	7
Effects of exchange rate changes	12	(56)
Benefit obligation at end of year	2,581	2,411	2,469
Change in plan assets
Fair value of plan assets at beginning of year	2,410	2,593
Actual return on plan assets	337	(52)
Employer contributions (qualified plans)	9	19
Employer contributions (non-qualified plans)	0	0
Participant contributions	7	7
Benefits paid	(103)	(87)
Settlements	(12)	(16)
Effects of exchange rate changes	13	(54)
Other	0	0
Fair value of plan assets at end of year	2,661	2,410	$ 2,593
Funded status at end of year	$ 80	$ (1)