Employee Benefit Plans - Contributions and Assumptions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount		$ 66	$ 67	$ 74
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		144
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		135
2019		670
2020		554
2021		547
2022		560
2023		570
Years 2024-2028		2,790
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		57	$ 64
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		35
2019		35
2020		33
2021		32
2022		31
2023		30
Years 2024-2028		$ 130
Discount rate assumptions used to determine benefit obligations		4.10%	3.50%	3.90%
Discount rate assumptions used to determine net periodic benefit costs		3.50%	3.90%	4.10%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year		6.30%	6.80%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate		4.70%	4.80%
Year that the rate reaches the ultimate trend rate		2025	2026
Effect on total service and interest cost components - 1% increase		$ 2
Effect on total service and interest cost components - 1% decrease		(1)
Effect on post-retirement benefit obligation - 1% increase		33
Effect on post-retirement benefit obligation - 1% decrease		(29)
Other Postretirement Benefits Plan [Member] | Forecasted [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate assumptions used to determine net periodic benefit costs	4.10%
U.S. | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		27	$ 675
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		25
2019		394
2020		273
2021		260
2022		267
2023		269
Years 2024-2028		$ 1,195
Discount rate assumptions used to determine benefit obligations		4.20%	3.60%	4.00%
Rate of compensation increase assumptions used to determine benefit obligation		0.20%	0.20%	0.20%
Discount rate assumptions used to determine net periodic benefit costs		3.60%	4.00%	4.30%
Expected return on plan assets assumptions used to determine net periodic benefit cost		5.80%	7.00%	7.50%
Rate of compensation increase assumptions used to determine net periodic benefit cost		0.20%	0.20%	0.20%
U.S. | Pension Plan [Member] | Forecasted [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate assumptions used to determine net periodic benefit costs	4.20%
Expected return on plan assets assumptions used to determine net periodic benefit cost	6.00%
Rate of compensation increase assumptions used to determine net periodic benefit cost	0.20%
U.S. | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 0
U.S. | Pension Plan [Member] | Qualified Plan [Member] | Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		0
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		0
U.S. | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		20
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		117	$ 161
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		110
2019		276
2020		281
2021		287
2022		293
2023		301
Years 2024-2028		$ 1,595
Discount rate assumptions used to determine benefit obligations		2.60%	2.30%	2.50%
Rate of compensation increase assumptions used to determine benefit obligation		2.60%	2.60%	2.60%
Discount rate assumptions used to determine net periodic benefit costs		2.30%	2.50%	3.30%
Expected return on plan assets assumptions used to determine net periodic benefit cost		3.80%	4.10%	4.80%
Rate of compensation increase assumptions used to determine net periodic benefit cost		2.60%	2.60%	2.70%
Foreign Plan [Member] | Pension Plan [Member] | Forecasted [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate assumptions used to determine net periodic benefit costs	2.60%
Expected return on plan assets assumptions used to determine net periodic benefit cost	4.00%
Rate of compensation increase assumptions used to determine net periodic benefit cost	2.60%