Employee Benefit Plans (Details 5) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effects of change in the assumed health care cost-trend rates
Effect on total service and interest cost components, 1 Percent Increase	$ 12
Effect on total service and interest cost components, 1 Percent Decrease	(10)
Effect on postretirement benefit obligation, 1 Percent Increase	188
Effect on postretirement benefit obligation, 1 Percent Decrease	$ (155)
Other Benefits
Assumptions used to determine benefit obligations:
Discount rate	3.80%	4.30%	4.60%
Assumptions used to determine net periodic benefit cost:
Discount rate for service cost	4.60%	4.90%	4.30%
Discount rate for interest cost	3.80%	4.00%	4.30%
U.S. | Pension Benefits
Assumptions used to determine benefit obligations:
Discount rate	3.50%	3.90%	4.00%
Rate of compensation increase	4.50%	4.50%	4.50%
Assumptions used to determine net periodic benefit cost:
Discount rate for service cost	4.20%	4.40%	3.70%
Discount rate for interest cost	3.00%	3.00%	3.70%
Expected return on plan assets	6.75%	7.25%	7.50%
Rate of compensation increase	4.50%	4.50%	4.50%
U.S. | Other Benefits
Assumptions used to determine benefit obligations:
Discount rate	3.60%	4.10%	4.50%
Int’l. | Pension Benefits
Assumptions used to determine benefit obligations:
Discount rate	3.90%	4.30%	5.30%
Rate of compensation increase	4.00%	4.50%	4.80%
Assumptions used to determine net periodic benefit cost:
Discount rate for service cost	4.30%	5.30%	5.00%
Discount rate for interest cost	4.30%	5.30%	5.00%
Expected return on plan assets	5.50%	6.30%	6.30%
Rate of compensation increase	4.50%	4.80%	5.10%