Commitment and Contingenices (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Commitments and Contingencies [Abstract]
Contingent Residual Support Agreement, Amount	$ 2,000
Accrued Environmental Loss Contingencies, Noncurrent		$ 2
Estimated litigation liability	$ 20	$ 21