Income Taxes - Summary of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 102,963	$ 67,958
Deferred revenue	2,240	1,732
Accrued bonus	2,963	1,822
Deferred rent	4,137	4,789
Nonaccrual receivables	8,437	9,353
Other	3,509	3,801
Research and development credits	12,512	9,534
Gross deferred tax assets	136,761	98,989
Deferred tax liability	(3,124)	(6,862)
Valuation allowance	(133,637)	(92,127)
Net deferred tax assets	$ 0	$ 0