At-The-Market Offering and Firm Commitment Offering At-The-Market Offering and Firm Commitment Offering (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Sale And Issue Of Shares Under Agreement [Line Items]
Total shares of common stock sold (in shares) | shares	33,084,151
Average price per share (in dollars per share) | $ / shares	$ 0.722
Gross proceeds	$ 23,877
Commissions earned by Cantor	152
Net Proceeds	$ 23,725
2019 ATM Offering
Sale And Issue Of Shares Under Agreement [Line Items]
Total shares of common stock sold (in shares) | shares	5,084,151
Average price per share (in dollars per share) | $ / shares	$ 0.999
Gross proceeds	$ 5,081
Commissions earned by Cantor	152
Net Proceeds	$ 4,929
Firm Commitment Offering
Sale And Issue Of Shares Under Agreement [Line Items]
Total shares of common stock sold (in shares) | shares	28,000,000
Average price per share (in dollars per share) | $ / shares	$ 0.6713
Gross proceeds	$ 18,796
Commissions earned by Cantor	0
Net Proceeds	$ 18,796