Net Parent Investment - Components of Net Transfers (to) from Parent on the Consolidated Statements of Cash Flows and Consolidated Statements of Equity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Net transfers (to) from Parent	$ (13)	$ 40	$ 3
Cash Pooling and General Financing Activities [Member]
Related Party Transaction [Line Items]
Net transfers (to) from Parent	(9)	(172)	(172)
Corporate Allocations [Member]
Related Party Transaction [Line Items]
Net transfers (to) from Parent		66	56
Income Taxes [Member]
Related Party Transaction [Line Items]
Net transfers (to) from Parent	$ (4)	$ 146	$ 119