Pension and Other Postretirement Benefit Plans - Accumulated and Projected Benefit Obligation in Excess of Plan Assets (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plans with a projected benefit obligation in excess of plan assets, projected benefit obligation	$ 13,013	$ 14,613
Pension plans with a projected benefit obligation in excess of plan assets, fair value of plan assets	12,072	12,672
Pension plans with an accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	12,916	13,489
Pension plans with an accumulated benefit obligation in excess of plan assets, fair value of plan assets	12,072	11,685
International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plans with a projected benefit obligation in excess of plan assets, projected benefit obligation	2,507	8,875
Pension plans with a projected benefit obligation in excess of plan assets, fair value of plan assets	1,731	7,488
Pension plans with an accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	2,462	4,234
Pension plans with an accumulated benefit obligation in excess of plan assets, fair value of plan assets	$ 1,723	$ 2,995