Fair Value Measurement - Additional Information (Detail) - USD ($)					1 Months Ended		3 Months Ended	9 Months Ended
	Jan. 10, 2020	May 30, 2019	Mar. 19, 2019	Feb. 12, 2019	Mar. 31, 2019	Feb. 28, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed asset purchases as right-of-use asset finance lease obligations								$ 1,073,000	$ 583,000
Estimated grant date fair value of warrants	$ 2.80		$ 10.10	$ 9.50
Issuance of unregistered warrants to purchase shares of common stock, grant date fair value	$ 1,900,000		$ 6,000,000	$ 6,800,000
Exercise price of unregistered warrants	$ 3.495		$ 12.50	$ 12.00		$ 12.00
Class of warrant or rights, term			5 years 6 months
Adjusted exercise price of warrants					$ 12.50	12.00
Estimated fair value of warrants					2.70	2.70
Estimated fair value of warrants increased					$ 3.00	$ 2.90
Warrants eligible for price modification					476,000	216,725
Warrant inducement expense					$ 130,000	$ 60,000	$ 1,800,000	2,100,000	$ 1,800,000
Follow-on Public Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Exercise price of unregistered warrants	$ 3.495		$ 12.50	$ 12.00
Class of warrant or rights, term	5 years 6 months		5 years 6 months	5 years
Warrant Inducement Transaction [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated grant date fair value of warrants		$ 11.80
Issuance of unregistered warrants to purchase shares of common stock, grant date fair value		$ 1,800,000
Exercise price of unregistered warrants		$ 13.10
Class of warrant or rights, term		5 years 6 months
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Issuance of unregistered warrants to purchase shares of common stock	692,725		595,000	716,500
Maximum [Member] | Warrant Inducement Transaction [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Issuance of unregistered warrants to purchase shares of common stock		154,722
Estimated Fair Value Measurements, Nonrecurring [Member] | Level 3 Inputs [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed asset purchases as right-of-use asset finance lease obligations								$ 1,073,000