Income Taxes - Summary of Tax Provisions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Pretax income at estimated annual effective income tax rate before discrete items	$ 52	$ 60	$ 106	$ 214
Catch-up adjustment to revalue previous quarter pre-tax income at current estimated annual effective tax rate	1	0	0	0
Interim period treatment of operational losses in foreign jurisdictions for which no tax benefit is recognized	0	(3)	1	4
Other discrete items	21	0	23	1
Provision for income taxes	$ 74	$ 57	$ 130	$ 219