Benefit Plans - Pension Plans Resulted in Net Pension Liability (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Prepaid pension assets	$ 132	$ 158
Other current liabilities	(25)	(59)
Accrued pension costs	(1,221)	(1,669)
Total	(1,114)	(1,570)
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Total	(1,114)	(1,570)
Pension Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	52	94
Accumulated benefit obligation	50	90
Fair value of plan assets	2	2
Pension Plans | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	3,343	9,345
Accumulated benefit obligation	3,194	9,138
Fair value of plan assets	$ 2,169	$ 7,709