Related Party Transactions and Parent Company Investment - Summary of Net Transfers from Parent on the Condensed Combined Statements of Equity (Parenthetical) (Detail) - USD ($) $ in Billions	1 Months Ended	3 Months Ended
	Dec. 31, 2016	Jan. 31, 2017
Parent Company [Member]
Related Party Transaction [Line Items]
Funding payments from parent	$ 1.9	$ 1.9