Stockholders' Equity - Additional Information (Details) - USD ($)		1 Months Ended			3 Months Ended			6 Months Ended
	Nov. 05, 2019	May 31, 2020	Apr. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2019	Nov. 30, 2019
Public Stock Offering
Class of Stock [Line Items]
Gross proceeds from public offering			$ 57,600,000
Consideration received from sale of stock			$ 53,700,000
Shares issued and sold (in shares)			25,587,500
Offering price (in dollars per share)			$ 2.25
Aspire Capital
Class of Stock [Line Items]
Equity purchase agreement, value	$ 100,000,000.0
Common stock issued as commitment fees (in shares)									350,000
Common stock registered for resale (in shares)									31,000,000
Net proceeds from sales of common stock						$ 10,200,000	$ 5,100,000	$ 10,700,000
Aspire Capital | Common Stock
Class of Stock [Line Items]
Issuance of common stock, new issues (in shares)					0	6,825,000	3,350,000	7,175,000
Sale of additional shares at an average price (in dollars per share)						$ 1.50	$ 1.52	$ 1.49
Healios
Class of Stock [Line Items]
Common stock issued upon exercise of warrant (in shares)				4,000,000
Common stock issued, price per share (in dollars per share)				$ 1.76
Proceeds from exercise of warrant			$ 7,000,000.0
Healios | Securities Purchase Agreement
Class of Stock [Line Items]
Consideration received from sale of stock		$ 534,105
Shares issued and sold (in shares)		310,526
Offering price (in dollars per share)		$ 1.72