Stockholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended			6 Months Ended
	Jan. 08, 2018	Jan. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stockholders Equity Note [Line Items]
Net proceeds from public offering						$ 76,595,000	$ 6,783,000
Common Stock
Stockholders Equity Note [Line Items]
Common stock, number of shares issued			1,471,000	17,867,000	1,978,000
Underwritten Public Offering | Common Stock
Stockholders Equity Note [Line Items]
Net proceeds from public offering		$ 62,700,000
Common stock, shares issued and sold		16,866,667
Common stock, par value		$ 0.001
Common stock, sale of stock, price per share		$ 3.75
Cantor Fitzgerald & Co | Amendment No. 3 | Sales Agreement
Stockholders Equity Note [Line Items]
Maximum common stock offering price	$ 70,000,000.0
Percentage of proceeds payable as compensation to underwriter	2.00%
Unsold shares of common stock, value	$ 31,400,000
Common stock, number of shares issued						2,500,000
Net proceeds from public offering						$ 13,900,000
Common stock registered for sale			$ 0			$ 0