Income Taxes - Summary of Tax Provisions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Pretax income at estimated annual effective income tax rate before discrete items	$ 53	$ 154
Interim period treatment of operational losses in foreign jurisdictions for which no tax benefit is recognized	1	7
Other discrete items	2	1
Provision for income taxes	$ 56	$ 162