Cash, Cash Equivalents and Restricted Cash - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents		$ 520		$ 390
Restricted cash and cash equivalents	[1]	325		18
Total cash, cash equivalents and restricted cash shown in the Consolidated Statements of Cash Flows		$ 845	[2]	$ 408	[2]	$ 612	$ 782

[1] Our restricted cash balances primarily served as cash collateral deposits for our letter of credit facilities. See Note 13, Debt, for further discussion.

[2] Our December 31, 2018 total Cash, cash equivalents and restricted cash included $248 million associated with the Combination.