Retirement Plans and Other Retiree Benefits - Summary of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Retiree Benefit Plans
Components of Net Periodic Benefit Cost
Service cost	$ 16	$ 13	$ 13
Interest cost	38	40	43
Annual ESOP allocation	0	0	0
Expected return on plan assets	(2)	0	(1)
Amortization of transition and prior service costs (credits)	0	0	0
Amortization of actuarial loss	14	13	14
Net periodic benefit cost	66	66	69
Other postretirement charges	0	(3)	1
Total pension cost	$ 66	$ 63	$ 70
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost
Discount rate	3.80%	4.41%	4.97%
Long-term rate of return on plan assets	6.60%	6.80%	6.80%
Long-term rate of compensation increase	0.00%	0.00%	0.00%
ESOP growth rate	10.00%	10.00%	10.00%
Medical cost trend rate of increase	6.00%	6.33%	6.67%
United States | Pension Plans
Components of Net Periodic Benefit Cost
Service cost	$ 1	$ 1	$ 1
Interest cost	86	94	105
Annual ESOP allocation	0	0	0
Expected return on plan assets	(115)	(111)	(109)
Amortization of transition and prior service costs (credits)	0	0	0
Amortization of actuarial loss	47	48	41
Net periodic benefit cost	19	32	38
Other postretirement charges	9	24	3
Total pension cost	$ 28	$ 56	$ 41
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost
Discount rate	3.73%	4.27%	4.93%
Long-term rate of return on plan assets	6.60%	6.80%	6.80%
Long-term rate of compensation increase	3.50%	3.50%	3.50%
ESOP growth rate	0.00%	0.00%	0.00%
Medical cost trend rate of increase	0.00%	0.00%	0.00%
Defined Benefit Plan Disclosure, Additional Information [Abstract]
Voluntary contributions to postretirement plans	$ 67	$ 81	$ 53
International | Pension Plans
Components of Net Periodic Benefit Cost
Service cost	14	16	16
Interest cost	21	22	25
Annual ESOP allocation	0	0	0
Expected return on plan assets	(21)	(22)	(23)
Amortization of transition and prior service costs (credits)	0	0	0
Amortization of actuarial loss	8	10	8
Net periodic benefit cost	22	26	26
Other postretirement charges	2	4	11
Total pension cost	$ 24	$ 30	$ 37
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost
Discount rate	2.53%	2.59%	3.17%
Long-term rate of return on plan assets	4.04%	4.14%	4.62%
Long-term rate of compensation increase	2.79%	2.58%	2.78%
ESOP growth rate	0.00%	0.00%	0.00%
Medical cost trend rate of increase	0.00%	0.00%	0.00%
Global Growth and Efficiency Program
Defined Benefit Plan Disclosure, Additional Information [Abstract]
Charges against assets	$ 27	$ 40	$ 33
Global Growth and Efficiency Program | Employee-Related Costs
Defined Benefit Plan Disclosure, Additional Information [Abstract]
Charges against assets	$ 9	$ 21	$ 4