Income Taxes - Summary of Tax Provisions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Pretax income at estimated annual effective income tax rate before discrete items	$ 66	$ 49	$ 170	$ 264
Catch-up adjustment to revalue previous quarter pre-tax income at current estimated annual effective tax rate	(2)	1	0	0
Interim period treatment of operational losses in foreign jurisdictions for which no tax benefit is recognized	(2)	1	(1)	5
Other discrete items	26	2	49	3
Provision for income taxes	$ 88	$ 53	$ 218	$ 272