Description of the Business and Liquidity (Details) - USD ($)	3 Months Ended
	Dec. 31, 2019	Mar. 31, 2020
Liquidity
Accumulated deficit	$ 235,574,000	$ 263,126,000
Net proceeds from issuance of common stock and preferred stock	$ 65,700,000
Public Offering
Liquidity
Issuance of stock (in shares)	32,200,000
2017 Equity Distribution Agreement
Liquidity
Net proceeds from issuance of common stock	$ 2,100,000
Issuance of shares under equity distribution agreement (in shares)	1,692,289
Series A Convertible Preferred Stock | Private placement
Liquidity
Issuance of Series A convertible preferred stock (in shares)	$ 30,000