Income Taxes - Schedule of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 72,752	$ 50,723
Research and development tax credit carryforwards	36,602	32,522
Capitalized organization costs	244	275
Stock-based compensation expense	12,783	9,178
Lease Liability	5,500
Charitable Contributions	13	11
Deferred Revenue	32,713	37,499
Accrued expenses	1,251	4,279
Capitalized research and development expenses	58	66
Total deferred tax assets	161,916	134,553
Deferred tax liabilities:
Depreciation and amortization	(1,467)	(2,544)
Right of use assets	(3,103)
Total deferred tax liabilities	(4,570)	(2,544)
Valuation allowance	$ (157,346)	$ (132,009)	$ (94,126)	$ (82,994)