Warrants (Fair Value of Warrants) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Fair Value	$ 11,830		$ 4,622
Change in Fair Value of common stock warrant liability	(7,208)	$ (20)
2018 January and February Issuance [Member]
Class of Warrant or Right [Line Items]
Fair Value	8,234		3,577
2017 May issuance [Member]
Class of Warrant or Right [Line Items]
Fair Value	$ 3,596		$ 1,045