Income Taxes - Accrual for Unrecognized Tax Benefits (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]
Balance at beginning of year	$ 97	$ 103	$ 121
Increases in estimates of tax positions related to prior fiscal year	1	0	0
Increases due to tax positions taken during the current year	0	6	3
Decreases relating to settlements with tax authorities	(5)	(10)	(19)
Decreases resulting from the lapse of applicable statutes of limitation	0	0	0
Net increases (decreases) due to translation and interest	2	(2)	(2)
Balance at end of year	$ 95	$ 97	$ 103