Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated other Comprehensive Income	Accumulated Deficit	Total
Beginning Balance at Dec. 31, 2018		$ 6	$ 5	$ 838,984	$ (42)	$ (372,760)	$ 466,193
Beginning Balance (in Shares) at Dec. 31, 2018	194	5,854,845	123,415,576
Stock-based compensation expense				5,846			5,846
Vesting of restricted shares issued for services			$ 1				1
Vesting of restricted shares issued for services (in shares)			7,037
Tax payments related to shares withheld for vested restricted stock units				(71)			(71)
Common stock issued upon exercise of stock options			$ 0	69			69
Common stock issued upon exercise of stock options (in shares)			5,000
Unrealized gain on short-term investments					180		180
Cancellation of common shares from settlement of dispute			$ (1)	(335)			(336)
Cancellation of common shares from settlement of dispute (In Shares)			(32,500)
Net loss						(36,950)	(36,950)
Ending Balance at Mar. 31, 2019		$ 6	$ 5	844,789	138	(410,006)	434,932
Ending Balance (in Shares) at Mar. 31, 2019	194	5,854,845	123,395,113
Adoption of ASU 2018-07				296		(296)
Beginning Balance at Dec. 31, 2019		$ 4	$ 5	869,354	220	(570,612)	298,971
Beginning Balance (in Shares) at Dec. 31, 2019	194	3,581,119	126,411,808
Stock-based compensation expense				9,412			9,412
Vesting of restricted shares issued for services (in shares)			7,273
Tax payments related to shares withheld for vested restricted stock units				(118)			(118)
Common stock issued upon exercise of stock options				3,951			3,951
Common stock issued upon exercise of stock options (in shares)			404,075
Unrealized gain on short-term investments					692		692
Net loss						(69,595)	(69,595)
Ending Balance at Mar. 31, 2020		$ 4	$ 5	$ 882,599	$ 912	$ (640,207)	$ 243,313
Ending Balance (in Shares) at Mar. 31, 2020	194	3,581,119	126,823,156