Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Line Items]
Effective tax rate	0.00%	0.00%	(4.00%)
Deferred tax assets, valuation allowance	$ 24,888	$ 15,420
Change in valuation allowance	9,468	8,132	$ 6,916
Federal net operating loss carry-forwards	63,309
State net operating loss carry-forwards	$ 81,436
Minimum maturity period for federal net operating loss carry-forward	5 years
Maximum maturity period for federal net operating loss carry-forward	20 years
Minimum maturity period for state net operating loss carry-forward	5 years
Maximum maturity period for state net operating loss carry-forward	20 years
Federal research and experimental tax credits	$ 4,303
State research and experimental tax credits	$ 1,390
Minimum maturity period for federal research and experimental tax credit carry-forward	5 years
Maximum maturity period for federal research and experimental tax credit carry-forward	20 years
Minimum maturity period for state research and experimental tax credit carry-forward	5 years
Maximum maturity period for state research and experimental tax credit carry-forward	20 years
Accrued interest and penalties associated with uncertain tax positions	$ 0	4	$ 6
2014 Offset Tax Liability [Member]
Income Tax Disclosure [Line Items]
Tax refund		$ 1,300