Income Taxes Uncertain Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits Excluding Amounts Pertaining to Examined Tax Returns RollForward [Abstract]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 34
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	57	$ 62	$ 69
Additions for tax positions related to current year	2	7	4
Reductions for tax positions taken in prior years	5	(1)	(1)
Additions for tax positions as a result of settlements	0	0	1
Reductions for tax positions as a result of lapse of statute of limitations	(14)	(11)	(11)
Ending Balance	50	57	$ 62
Increases (decreases) for interest and penalties	$ 7	$ 6