Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment reporting_unit	Sep. 30, 2018 USD ($)	Mar. 13, 2019 USD ($)	Jan. 01, 2019 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Minimum liquidity as a percentage of debt	125.00%		125.00%
Maximum liquidity other than cash and cash equivalents	$ 2,500,000		$ 2,500,000
Debt instrument covenant liquidity in cash	25,000,000		$ 25,000,000
Number of operating segments | segment			1
Number of reporting units | reporting_unit			1
Fair value of derivative liability					$ 5,200,000
Currency translation adjustments	(77,000)	$ 0	$ (119,000)	$ 0
Operating lease liabilities	3,025,000		3,025,000
Right-of-use assets	$ 2,110,000		$ 2,110,000
Accounting Standards Update 2016-02
Restricted Cash and Cash Equivalents Items [Line Items]
Operating lease liabilities						$ 2,500,000
Right-of-use assets						$ 2,000,000.0
Arsanis
Restricted Cash and Cash Equivalents Items [Line Items]
Fair value of derivative liability					$ 0