Retirement Plans and Other Retiree Benefits - Expected Contributions and Benefit Payments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Estimated future voluntary employer contributions in next fiscal year	$ 100
Expected benefit payments from company assets	61
Total benefit payments [Abstract]
2019	231
2020	228
2021	232
2022	235
2023	240
2024-2028	1,209
Other Retiree Benefit Plans
Total benefit payments [Abstract]
2019	47
2020	47
2021	48
2022	48
2023	49
2024-2028	256
United States | Pension Plans
Total benefit payments [Abstract]
2019	149
2020	146
2021	147
2022	151
2023	151
2024-2028	736
International | Pension Plans
Total benefit payments [Abstract]
2019	35
2020	35
2021	37
2022	36
2023	40
2024-2028	$ 217