Balance Sheet Components - Activities of Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning Balance	$ 15,675	$ 10,352	$ 9,466
Provision for allowance for doubtful accounts	5,627	8,260	5,037
Net write-offs	(4,546)	(2,521)	(3,438)
Impact of foreign currency exchange	1,472	(416)	(713)
Ending Balance	$ 18,228	$ 15,675	$ 10,352