Organization, Basis of Presentation and Summary of Significant Accounting Policies - Condensed Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Organization And Summary Of Significant Accounting Policies [Line Items]
Net loss	$ (36,827)	$ (29,123)
Changes in deferred revenue	138,474	$ 64,346
Adjustments [Member] | Topic 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Net loss	(4,047)
Changes in deferred revenue	4,047
Balances without adoption of Topic 606 [Member] | Topic 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Net loss	(40,874)
Changes in deferred revenue	$ 142,521