Employee Benefit Plans - Accumulated Benefit Obligation in Excess of Plan Assets (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
U.S.
Pension Plans With Accumulated Benefit Obligation in Excess of Plan Assets
Projected benefit obligations	$ 14,401	$ 11,667
Accumulated benefit obligations	12,718	10,456
Fair value of plan assets	10,091	8,456
Int’l.
Pension Plans With Accumulated Benefit Obligation in Excess of Plan Assets
Projected benefit obligations	1,554	1,277
Accumulated benefit obligations	1,268	1,062
Fair value of plan assets	$ 278	$ 198