Revenue Recognition - Summary of Impact of New Revenue Recognition Guidance on Unaudited Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue (Note 3)	$ 378	$ 372
Operating income	23	27
Income before income taxes	21	25
Provision for income taxes	(16)	(12)
Net income	5	$ 13
ASC 606 | Impact of Accounting Under ASC 606
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue (Note 3)	(4)
Operating income	(4)
Income before income taxes	(4)
Provision for income taxes	1
Net income	(3)
ASC 606 | Adjusted - ASC 605
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue (Note 3)	374
Operating income	19
Income before income taxes	17
Provision for income taxes	(15)
Net income	$ 2