CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total		Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning balances at Dec. 31, 2017	$ 21,544		$ 20,966	$ 3	$ 633,436	$ (7)	$ (632,854)
Issuance of common stock through controlled equity offering facilities, net of issuance cost					32
Issuance of common stock pursuant to stock option exercises					164
Issuance of common stock from vesting of restricted stock awards, net of shares withheld for taxes					83
Stock-based compensation expenses					813
Unrealized gain on available-for-sale securities	2					2
Net loss	(7,273)						(7,273)
Ending balances at Mar. 31, 2018	15,365		20,966	3	634,528	$ (5)	(640,127)
Beginning balances at Dec. 31, 2018	3,993	[1]	20,998	4	642,460		(659,469)
Issuance of preferred stock in underwritten offering, net of issuance costs			7,877		10,656
Issuance of common stock in underwritten offering, net of issuance costs				2	3,228
Conversion of preferred stock to common stock			(3,228)	1
Issuance of common stock from vesting of restricted stock awards, net of shares withheld for taxes					54
Stock-based compensation expenses					363
Net loss	(5,860)						(5,860)
Ending balances at Mar. 31, 2019	$ 17,086		$ 25,647	$ 7	$ 656,761		$ (665,329)

[1] The condensed consolidated balance sheet as of December 31, 2018, has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018.