Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Sep. 17, 2020	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Sep. 11, 2020	Jul. 27, 2020	Nov. 08, 2019
Class of Stock [Line Items]
Reverse stock split			1-for-5
Common Stock, shares authorized upon the completion of the IPO			225,000,000	225,000,000	225,000,000
Common stock, par value			$ 0.001	$ 0.001
Common share issued			51,626,508	22,806,890
Total proceeds			$ 139,760	$ 185
Common stock, shares outstanding			51,626,508	22,806,890
Lincoln Park Capital Purchase Agreement [Member]
Class of Stock [Line Items]
Common stock, par value							$ 0.001
Value of right to sell number of shares							$ 20,000
Common share issued		140,000					141,318
Total proceeds		$ 300
Private Placement [Member]
Class of Stock [Line Items]
Common stock, par value			$ 4.35
Total proceeds			$ 71,800
Company issued shares			16,505,743
2020 Underwritten Public Offering [Member]
Class of Stock [Line Items]
Shares issued in public offering	9,200,000
Warrants to purchase common stock	78,200,000
2020 Underwritten Public Offering [Member] | J.P. Morgan Securities LLC and Jefferies LLC [Member]
Class of Stock [Line Items]
Shares issued in public offering	8,000,000
Warrants to purchase common stock	1,200,000
Controlled Equity OfferingSM Sales Agreement [Member] | Cantor Fitzgerald & Co. [Member]
Class of Stock [Line Items]
Common stock, par value			$ 0.001
Total proceeds			$ 100,000
2020 Equity Plan [Member]
Class of Stock [Line Items]
Shares available for future grant			6,349,911		7,000,000	7,000,000
Percentage of outstanding shares approved equity plan						63.00%
Maximum [Member]
Class of Stock [Line Items]
Common stock, shares outstanding					210,900,000
Minimum [Member]
Class of Stock [Line Items]
Common stock, shares outstanding					42,200,000