New Revenue Recognition Standard - Condensed Consolidated Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ 13,744	$ (20,852)	$ (2,074)	$ (44,398)
Changes in operating assets and liabilities:
Accounts receivable, net			5,087	(2,105)
Deferred revenue			0	$ (700)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	1,109		1,626
Changes in operating assets and liabilities:
Accounts receivable, net			(38)
Deferred revenue			1,588
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ 14,853		(448)
Changes in operating assets and liabilities:
Accounts receivable, net			5,049
Deferred revenue			$ 1,588