Income Taxes Reconciliation of Changes in Unrecognized Tax Benefits Liabilities / (Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 69	$ 78	$ 56
Additions for tax positions related to current year	4	7	16
Additions for tax positions taken in prior years			13
Reductions for tax positions taken in prior years	(1)	(8)
Additions for tax positions as a result of settlements	1	1
Reductions for tax positions as a result of settlements			(1)
Reductions for tax positions as a result of lapse of statute of limitations	(11)	(9)	(6)
Ending Balance	62	$ 69	$ 78
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 31