Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	20.10%			2.00%	1.10%	(49.80%)
Provisional income tax expense			$ 345
Reduction in provisional expense for remeasurement of deferred taxes		$ 11
Increase in provisional expense for transition tax	$ 24
Effect of change to provisional transition tax (percentage)	12.40%				2.90%