Net Loss per Share - Additional Information (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Apr. 16, 2019	Apr. 12, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding—basic and diluted (in shares)	14,562,000	459,000	9,866,000	459,000
Pre Funded Warrant
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding—basic and diluted (in shares)	2,130,000		2,130,000
Exercise Price (usd per share)					$ 10.999	$ 10.999
Pre Funded Warrant | Maximum
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Exercise Price (usd per share)	$ 0.01		$ 0.01
Redeemable Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding—basic and diluted (in shares)		107,371	107,371	107,371