Pension and Other Postretirement Benefit Plans (Accumulated Benefit Obligation in Excess of Plan Assets) (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
United States Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected benefit obligation	$ 2,622	$ 3,033
Accumulated benefit obligation	2,609	3,022
Fair value of plan assets	2,409	2,676
Foreign Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected benefit obligation	800	720
Accumulated benefit obligation	776	699
Fair value of plan assets	$ 450	$ 396