Fair Value - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) $ / shares	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Apr. 28, 2017 USD ($) $ / shares shares
Fair Value Measurements Disclosure [Line Items]
Transfers of assets between Level 1, Level 2, and Level 3 of the fair value hierarchy	$ 0		$ 0		$ 0
Transfers of liabilities between Level 1, Level 2, and Level 3 of the fair value hierarchy	0		0		0
Fair value of contingent consideration			2,000,000.0	$ 1,400,000
Warrants to purchase common shares (in units) | shares						24,900,000
Offering price (in dollars per share) | $ / shares						$ 1.00
Change in fair value of warrant liabilities	2,528,000	$ (17,507,000)	2,422,000	$ (15,678,000)
Series A Warrant
Fair Value Measurements Disclosure [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares						$ 1.00
Series A Warrant | Black-Scholes Merton Model
Fair Value Measurements Disclosure [Line Items]
Estimated fair value of warrants						$ 2,500,000
Fair value input, share price (in dollars per share) | $ / shares						$ 0.65
Series A Warrant | Black-Scholes Merton Model | Measurement Input, Expected Term
Fair Value Measurements Disclosure [Line Items]
Fair value input, term						1 year
Series A Warrant | Black-Scholes Merton Model | Measurement Input, Risk Free Interest Rate
Fair Value Measurements Disclosure [Line Items]
Fair value input, risk free rate						0.0107
Series A Warrant | Black-Scholes Merton Model | Measurement Input, Expected Dividend Payment
Fair Value Measurements Disclosure [Line Items]
Fair value input, risk free rate						0
Series A Warrant | Black-Scholes Merton Model | Measurement Input, Price Volatility
Fair Value Measurements Disclosure [Line Items]
Fair value input, risk free rate						0.7314
Series B Warrant
Fair Value Measurements Disclosure [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares						$ 1.00
Estimated fair value of warrants	$ 2,200,000		$ 2,200,000		$ 4,600,000	$ 6,200,000
Fair value input, share price (in dollars per share) | $ / shares	$ 1.36		$ 1.36		$ 2.26	$ 0.65
Series B Warrant | Measurement Input, Expected Term
Fair Value Measurements Disclosure [Line Items]
Fair value input, term	2 years 9 months 18 days		2 years 9 months 18 days		3 years 3 months 18 days	5 years
Series B Warrant | Measurement Input, Risk Free Interest Rate
Fair Value Measurements Disclosure [Line Items]
Fair value input, risk free rate	0.0171		0.0171		0.0247	0.0181
Series B Warrant | Measurement Input, Price Volatility
Fair Value Measurements Disclosure [Line Items]
Fair value input, risk free rate	0.8234		0.8234		0.876	0.7314
Common Stock
Fair Value Measurements Disclosure [Line Items]
Number of common stock or warrants in each unit (in shares) | shares						1
Common Stock | Series A Warrant
Fair Value Measurements Disclosure [Line Items]
Number of common stock or warrants in each unit (in shares) | shares						1
Common Stock | Series B Warrant
Fair Value Measurements Disclosure [Line Items]
Number of common stock or warrants in each unit (in shares) | shares						0.75