Cash, Cash Equivalents and Restricted Cash - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents		$ 800	$ 520
Restricted cash and cash equivalents	[1]	393	325
Total cash, cash equivalents and restricted cash shown in the Statements of Cash Flows		$ 1,193	$ 845	$ 408	$ 612

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