Income Taxes - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Total provision (benefit) from income taxes	$ 345
Transition tax payable	264	$ 240	$ 264
Estimated transition tax			264
Estimated tax expense for the re-measurement of deferred tax assets and liabilities			$ 86
Statutory tax rate		19.00%	19.30%	20.00%
Decrease in valuation allowance		$ 35
Benefit realized from tax holiday granted		$ 77	$ 45	$ 46
Earnings per share impact of tax holiday (in dollars per share)		$ 0.31	$ 0.17	$ 0.17
Unrecognized tax benefits that would impact effective tax rate	219	$ 228	$ 219	$ 240
Accrued potential interest and penalties		22	11	15
Liability recorded for interest and penalties	55	77	55	$ 48
Unremitted earnings	$ 39	$ 30	$ 39