Leases - Schedule of Leases (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Assets
Operating lease assets	$ 2,193
Total leased assets	2,193
Liabilities
Current - Operating	574
Noncurrent - Operating	1,771
Total leased liabilities	2,345
Lease Cost
Net lease cost	$ 208
Lease Term and Discount Rate
Weighted-average remaining lease term (years)	2 years 7 months 6 days
Weighted-average discount rate	7.00%
SG&A and R&D Expenses [Member]
Lease Cost
Operating lease cost	$ 175
Sublease income	(15)
R&D Expenses [Member]
Lease Cost
Short term lease cost	$ 48

Operating lease assets.

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Operating lease assets.

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Operating lease liabilities.

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Operating lease term and discount rate.

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Amount of lease cost recognized by lessee for lease contract.

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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Present value of lessee's discounted obligation for lease payments from operating lease.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

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Amount of lessee's right to use underlying asset under operating lease.

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Weighted average discount rate for operating lease calculated at point in time.

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Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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Amount of sublease income excluding finance and operating lease expense.

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