Organization and Summary of Significant Accounting Policies - Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Organization and Summary of Significant Accounting Policies [Line Items]
Net loss	$ (18,664)	$ (12,843)	$ (16,640)	$ (20,187)	$ (13,091)	$ (12,354)	$ (12,491)	$ (16,632)	$ (68,334)	$ (54,568)	$ (71,658)
Changes in deferred revenue									99,364	$ 48,984	$ (5,214)
Adjustments [Member] | Topic 606 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Net loss									(13,558)
Changes in deferred revenue									13,558
Balances without adoption of Topic 606 [Member] | Topic 606 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Net loss									(81,892)
Changes in deferred revenue									$ 112,922