Income Taxes Reconciliaton of Changes in Unrecognized Tax Benefits Liabilities / (Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 78	$ 56	$ 48
Additions for tax positions related to current year	7	16	16
Additions for tax positions taken in prior years		13	1
Reductions for tax positions taken in prior years	(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	(9)	(6)	(10)
Ending Balance	69	$ 78	$ 56
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 38