Unaudited Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member] Series C-1 Convertible Preferred Stock [Member]	Preferred Stock [Member] Series F Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings
Beginning Balance (in shares) at Dec. 31, 2018		4,000	3,000	26,259,000
Beginning Balance at Dec. 31, 2018	$ 35,921	$ 3,906	$ 2,737	$ 3	$ 950,258	$ (920,983)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	6,782				6,782
Issuance of common stock under ESPP (in shares)				52,000
Issuance of common stock under ESPP	283				283
Net loss	(31,685)					(31,685)
Issuance of common stock for conversion of Series F Preferred Stock (in shares)			(3,000)	782,000
Issuance of common stock for conversion of Series F Preferred Stock			$ (2,737)		2,737
Ending Balance (in shares) at Mar. 31, 2019		4,000	0	27,093,000
Ending Balance at Mar. 31, 2019	11,301	$ 3,906	$ 0	$ 3	959,900	(952,508)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	(160)
Beginning Balance (in shares) at Dec. 31, 2019		4,000	0	27,195,000
Beginning Balance at Dec. 31, 2019	(55,990)	$ 3,906	$ 0	$ 3	977,432	(1,037,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	$ 2,407
Exercise of stock options for common stock (in shares)	44,258			44,000
Exercise of stock options for common stock	$ 305				305
Issuance of common stock under ESPP (in shares)				38,000
Issuance of common stock under ESPP	200				200
Net loss	(8,591)					(8,591)
Ending Balance (in shares) at Mar. 31, 2020		4,000	0	27,277,000
Ending Balance at Mar. 31, 2020	(61,669)	$ 3,906	$ 0	$ 3	$ 980,344	$ (1,045,922)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	$ 0