Income Taxes - Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets Valuation Allowance [Roll Forward]
Balance at beginning of year	$ 79	$ 59	$ 84
Valuation allowances for unutilized net operating losses and excess foreign tax credits generated in the current year	45	25	11
Change in valuation allowances related to prior years	(20)	(2)	(16)
Write-off of valuation allowances and associated deferred tax assets for certain losses that have no possibility of being utilized	0	0	(19)
Effect of translation	(11)	(3)	(1)
Balance at end of year	$ 93	$ 79	$ 59