Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 81,039,000	$ 39,605,000
Uncertain income tax position, description	Under ASC Topic 740, the impact of an uncertain income tax position taken on a tax return must be recognized at the largest amount that is cumulatively “more likely than not” to be sustained upon audit by relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained.
Unrecognized tax benefits that would impact effective tax rate		$ 40,000
Interest recognized	$ 0
Significant change in uncertain tax positions in the next 12 months	0
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 13,200,000
Net operating loss carryforward, expiration year	2034
Foreign Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Research and development credits	$ 4,500,000
Foreign Tax Authority [Member] | Earliest Tax Year [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Research and development credits, expiration year	2029
Foreign Tax Authority [Member] | Latest Tax Year [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Research and development credits, expiration year	2036
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 39,200,000
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Research and development credits	$ 2,800,000
State and Local Jurisdiction [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward, expiration year	2029
State and Local Jurisdiction [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward, expiration year	2036