Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2018	$ (211,476)			$ 2	$ 13,261	$ (224,725)		$ (14)
Temporary equity, shares at Dec. 31, 2018			102,030
Temporary equity, balance at Dec. 31, 2018			$ 216,446
Balance, shares at Dec. 31, 2018				17,445
Exercise of stock options	132				132
Exercise of stock options, shares				96
Stock-based compensation	595				595
Accumulated dividend – Series F	(1,736)					(1,736)
Accretion of Series F issuance costs	(18)				(18)
Net loss	(10,541)					(10,541)
Balance at Mar. 31, 2019	(223,044)			$ 2	13,970	(237,002)		(14)
Temporary equity, shares at Mar. 31, 2019			102,030
Temporary equity, balance at Mar. 31, 2019			$ 218,200
Balance, shares at Mar. 31, 2019				17,541
Temporary Equity, Accumulated dividend – Series F			1,736
Temporary Equity, Accretion of Series F issuance costs			$ 18
Balance at Dec. 31, 2018	(211,476)			$ 2	13,261	(224,725)		(14)
Temporary equity, shares at Dec. 31, 2018			102,030
Temporary equity, balance at Dec. 31, 2018			$ 216,446
Balance, shares at Dec. 31, 2018				17,445
Net loss	(21,573)
Balance at Jun. 30, 2019	(235,013)			$ 2	14,813	(249,814)		(14)
Temporary equity, shares at Jun. 30, 2019			102,030
Temporary equity, balance at Jun. 30, 2019			$ 219,998
Balance, shares at Jun. 30, 2019				17,901
Balance at Mar. 31, 2019	(223,044)			$ 2	13,970	(237,002)		(14)
Temporary equity, shares at Mar. 31, 2019			102,030
Temporary equity, balance at Mar. 31, 2019			$ 218,200
Balance, shares at Mar. 31, 2019				17,541
Exercise of stock options	40				40
Exercise of stock options, shares				360
Stock-based compensation	821				821
Accumulated dividend – Series F	(1,780)					(1,780)
Accretion of Series F issuance costs	(18)				(18)
Net loss	(11,032)					(11,032)
Balance at Jun. 30, 2019	(235,013)			$ 2	14,813	(249,814)		$ (14)
Temporary equity, shares at Jun. 30, 2019			102,030
Temporary equity, balance at Jun. 30, 2019			$ 219,998
Balance, shares at Jun. 30, 2019				17,901
Temporary Equity, Accumulated dividend – Series F			1,780
Temporary Equity, Accretion of Series F issuance costs			$ 18
Balance at Dec. 31, 2019	$ (257,303)	$ (364)		$ 2	17,244	(274,549)	$ (364)
Temporary equity, shares at Dec. 31, 2019	102,030		102,030
Temporary equity, balance at Dec. 31, 2019			$ 223,754
Balance, shares at Dec. 31, 2019				18,544
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member					us-gaap:AccountingStandardsUpdate201613Member
Exercise of stock options	$ 404				404
Exercise of stock options, shares				448
Stock-based compensation	1,026				1,026
Accumulated dividend – Series F	(1,727)					(1,727)
Accretion of Series F issuance costs	(18)				(18)
Warrants issued in connection with debt	297				297
Net loss	(4,023)					(4,023)
Balance at Mar. 31, 2020	(261,708)			$ 2	18,953	(280,663)
Temporary equity, shares at Mar. 31, 2020			102,030
Temporary equity, balance at Mar. 31, 2020			$ 225,499
Balance, shares at Mar. 31, 2020				18,992
Temporary Equity, Accumulated dividend – Series F			1,727
Temporary Equity, Accretion of Series F issuance costs			$ 18
Balance at Dec. 31, 2019	$ (257,303)	$ (364)		$ 2	17,244	(274,549)	$ (364)
Temporary equity, shares at Dec. 31, 2019	102,030		102,030
Temporary equity, balance at Dec. 31, 2019			$ 223,754
Balance, shares at Dec. 31, 2019				18,544
Net loss	$ (12,504)
Balance at Jun. 30, 2020	$ (270,506)			$ 2	20,571	(291,079)
Temporary equity, shares at Jun. 30, 2020	102,030		102,030
Temporary equity, balance at Jun. 30, 2020			$ 227,452
Balance, shares at Jun. 30, 2020				19,378
Balance at Mar. 31, 2020	$ (261,708)			$ 2	18,953	(280,663)
Temporary equity, shares at Mar. 31, 2020			102,030
Temporary equity, balance at Mar. 31, 2020			$ 225,499
Balance, shares at Mar. 31, 2020				18,992
Exercise of stock options	366				366
Exercise of stock options, shares				351
Exercise of warrants	126				126
Exercise of warrants, shares				35
Stock-based compensation	1,144				1,144
Accumulated dividend – Series F	(1,935)					(1,935)
Accretion of Series F issuance costs	(18)				(18)
Net loss	(8,481)					(8,481)
Balance at Jun. 30, 2020	$ (270,506)			$ 2	$ 20,571	$ (291,079)
Temporary equity, shares at Jun. 30, 2020	102,030		102,030
Temporary equity, balance at Jun. 30, 2020			$ 227,452
Balance, shares at Jun. 30, 2020				19,378
Temporary Equity, Accumulated dividend – Series F			1,935
Temporary Equity, Accretion of Series F issuance costs			$ 18