Commitments and Contingencies Environmental (Details) - Environmental Issue [Member] $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) sites	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Number of alleged environmental contamination sites (in sites) | sites	213
Number of environmental superfund sites (in sites) | sites	18
Recorded Liability For Third Party Environmental Tort Claims	$ 9		$ 9
Accrued obligations for environmental matters, current liabilities	$ 40		$ 40
Years in which accrued environmental costs will be paid over	10
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 317	$ 342
Accruals / changes in estimates	1	1
Payments	(4)	(8)
Ending balance	314	$ 335
Minimum [Member]
Loss Contingencies [Line Items]
Future costs to settle claims and associated liability	255
Maximum [Member]
Loss Contingencies [Line Items]
Future costs to settle claims and associated liability	$ 415