Income Taxes - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Estimated transition tax	$ 264
Estimated tax expense for the re-measurement of deferred tax assets and liabilities	86
Decrease in valuation allowance	6
Undistributed earnings of foreign subsidiaries	3,200
Benefit realized from tax holiday granted	$ 45	$ 46	$ 23
Earnings per share impact of tax holiday (in dollars per share)	$ 0.17	$ 0.17	$ 0.08
Unrecognized tax benefits that would impact effective tax rate	$ 219	$ 240	$ 200
Accrued potential interest and penalties	11	15	2
Liability recorded for interest and penalties	55	$ 48	$ 33
Non-US [Member]
Operating Loss Carryforwards [Line Items]
Estimate of local country income and withholding on undistributed earnings	$ 39