Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Loss
Unamortized prior service credit, net of tax expense of $32 for 2018 and $76 for 2017	$ 98	$ 133
Cumulative translation adjustment	(144)	(136)
Other, net	(6)	4
Total accumulated other comprehensive loss	(52)	1
Unamortized benefit plan costs - Tax Benefit	32	76
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	$ 60	$ 44	$ 62