Postretirement Benefit Plans - Schedule of Change in AOCI (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Defined benefit plan amounts recognized in other comprehensive income net actuarial loss portion roll forward
AOCI balance, net actuarial loss portion (net of taxes), beginning of period	$ 542
Adjustments, net actuarial loss	(118)
Recognized within Net income, net actuarial loss	(83)
Tax effect, net actuarial loss	53
Total change to AOCI, net actuarial loss	(148)
AOCI balance, net actuarial loss portion (net of taxes), period end	394
Defined benefit plan amounts recognized in other comprehensive income prior service credit portion roll forward
AOCI balance, net prior service credit (net of taxes), beginning of period	(17)
Adjustments, prior service credit	3
Recognized within Net income, prior service credit	6
Tax effect, prior service credit	(2)
Total change to AOCI, prior service credit	7
AOCI balance, net prior service credit (net of taxes), period end	(10)
U.S. | Defined benefit plan
Defined benefit plan amounts recognized in other comprehensive income net actuarial loss portion roll forward
AOCI balance, net actuarial loss portion (net of taxes), beginning of period	133
Adjustments, net actuarial loss	28
Recognized within Net income, net actuarial loss	(51)
Tax effect, net actuarial loss	8
Total change to AOCI, net actuarial loss	(15)
AOCI balance, net actuarial loss portion (net of taxes), period end	118
U.S. | Retiree health care plan
Defined benefit plan amounts recognized in other comprehensive income net actuarial loss portion roll forward
AOCI balance, net actuarial loss portion (net of taxes), beginning of period	58
Adjustments, net actuarial loss	(41)
Recognized within Net income, net actuarial loss	(3)
Tax effect, net actuarial loss	15
Total change to AOCI, net actuarial loss	(29)
AOCI balance, net actuarial loss portion (net of taxes), period end	29
Defined benefit plan amounts recognized in other comprehensive income prior service credit portion roll forward
AOCI balance, net prior service credit (net of taxes), beginning of period	(11)
Adjustments, prior service credit	3
Recognized within Net income, prior service credit	4
Tax effect, prior service credit	(2)
Total change to AOCI, prior service credit	5
AOCI balance, net prior service credit (net of taxes), period end	(6)
Non-U.S. | Defined benefit plan
Defined benefit plan amounts recognized in other comprehensive income net actuarial loss portion roll forward
AOCI balance, net actuarial loss portion (net of taxes), beginning of period	351
Adjustments, net actuarial loss	(105)
Recognized within Net income, net actuarial loss	(29)
Tax effect, net actuarial loss	30
Total change to AOCI, net actuarial loss	(104)
AOCI balance, net actuarial loss portion (net of taxes), period end	247
Defined benefit plan amounts recognized in other comprehensive income prior service credit portion roll forward
AOCI balance, net prior service credit (net of taxes), beginning of period	(6)
Adjustments, prior service credit	0
Recognized within Net income, prior service credit	2
Tax effect, prior service credit	0
Total change to AOCI, prior service credit	2
AOCI balance, net prior service credit (net of taxes), period end	$ (4)