Benefit Plans (Accumulated Benefit Obligation) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 433	$ 384
Information for pension plans with an accumulated benefit obligation in excess of plan assets:
Projected benefit obligation	109	90
Accumulated benefit obligation	97	80
Fair value of plan assets	33	25
Information for pension plans with a projected benefit obligation in excess of plan assets:
Projected benefit obligation	238	212
Fair value of plan assets	154	142
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	1,236	1,167
Information for pension plans with an accumulated benefit obligation in excess of plan assets:
Projected benefit obligation	1,257	1,188
Accumulated benefit obligation	1,236	1,167
Fair value of plan assets	1,127	1,044
Information for pension plans with a projected benefit obligation in excess of plan assets:
Projected benefit obligation	1,257	1,188
Fair value of plan assets	$ 1,127	$ 1,044