Pension and Other Postretirement Benefits - About our Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United States [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Market-related valuation of pension plan assets	$ 4,000
Plan assets at fair value	4,151	$ 4,281	$ 3,977
Defined benefit plan cost	17	2	18
Defined benefit plan benefit obligation	4,741	4,969	4,888
United States [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	2	5
Defined benefit plan cost	7	7	9
Defined benefit plan benefit obligation	210	$ 258	$ 277
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Defined benefit plan cost
Defined benefit plan benefit obligation