Supplemental Balance Sheet Information - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Supplemental Balance Sheet Information [Line Items]
Prepaid other taxes	$ 67		$ 67		$ 194
Deferred Payment Arrangements [Member]
Supplemental Balance Sheet Information [Line Items]
Accounts receivable	61		61		55
Allowance for doubtful accounts, deferred payment arrangement	32		32		$ 30
Provision for doubtful accounts, accounts receivable	$ 1	$ 2	$ 2	$ 3