Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock Private Placement	Common Stock At-the-market sales	Common Stock	Additional Paid-in Capital Private Placement	Additional Paid-in Capital At-the-market sales	Additional Paid-in Capital	AOCI Attributable to Parent [Member]	Accumulated Deficit Private Placement	Accumulated Deficit At-the-market sales	Accumulated Deficit	Private Placement	At-the-market sales	Total
Balance at Dec. 31, 2018			$ 3			$ 261,722	$ (241,551)			$ 20,174
Balance (in shares) at Dec. 31, 2018			34,377,329
Increase (decrease) in stockholders' equity
Adjustment to derivative liabilities upon adoption of ASU 2017-11						213	(213)
Share-based compensation - stock options and RSUs						490				490
Issuance of common stock	$ 1			$ 7,809	$ 860			$ 7,810	$ 860
Issuance of common stock (in shares)	8,426,750	665,974
Vesting of RSUs (in shares)			145,204
Net loss							(4,669)			(4,669)
Balance at Mar. 31, 2019			$ 4			271,094	(246,433)			24,665
Balance (in shares) at Mar. 31, 2019			43,615,257
Balance at Dec. 31, 2018			$ 3			261,722	(241,551)			20,174
Balance (in shares) at Dec. 31, 2018			34,377,329
Increase (decrease) in stockholders' equity
Issuance of common stock (in shares)												1,658,046
Net loss													$ (8,153)
Balance at Jun. 30, 2019			$ 4			272,977	(249,917)			23,064
Balance (in shares) at Jun. 30, 2019			44,632,329
Balance at Mar. 31, 2019			$ 4			271,094	(246,433)			24,665
Balance (in shares) at Mar. 31, 2019			43,615,257
Increase (decrease) in stockholders' equity
Share-based compensation - stock options						479				479
Issuance of common stock					$ 1,389				$ 1,389
Issuance of common stock (in shares)		992,072
Issuance of common stock upon exercise of options						15				15
Issuance of common stock upon exercise of options (in shares)			25,000
Net loss							(3,484)			(3,484)			(3,484)
Balance at Jun. 30, 2019			$ 4			272,977	(249,917)			23,064
Balance (in shares) at Jun. 30, 2019			44,632,329
Balance at Dec. 31, 2019			$ 7			306,108				(260,370)			45,745
Balance (in shares) at Dec. 31, 2019			69,810,305
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs						621							621
Issuance of common stock	$ 2			$ 48,433							$ 48,435
Issuance of common stock (in shares)	17,250,000
Issuance of common stock upon exercise of options						119							119
Issuance of common stock upon exercise of options (in shares)			152,907
Warrant discount						3,570							3,570
Net loss										(7,883)			(7,883)
Balance at Mar. 31, 2020			$ 9			358,851				(268,253)			90,607
Balance (in shares) at Mar. 31, 2020			87,213,212
Balance at Dec. 31, 2019			$ 7			306,108				(260,370)			45,745
Balance (in shares) at Dec. 31, 2019			69,810,305
Increase (decrease) in stockholders' equity
Unrealized gain on marketable securities													10
Net loss													(18,709)
Balance at Jun. 30, 2020			$ 9			359,856	10			(279,079)			80,796
Balance (in shares) at Jun. 30, 2020			87,297,605
Balance at Mar. 31, 2020			$ 9			358,851				(268,253)			90,607
Balance (in shares) at Mar. 31, 2020			87,213,212
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs						839							839
Issuance of common stock upon exercise of options						166							166
Issuance of common stock upon exercise of options (in shares)			84,393
Unrealized gain on marketable securities							10						10
Net loss										(10,826)			(10,826)
Balance at Jun. 30, 2020			$ 9			$ 359,856	$ 10			$ (279,079)			$ 80,796
Balance (in shares) at Jun. 30, 2020			87,297,605