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	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	$ 35,921	$ 3,906	$ 2,737	$ 3	$ 950,258	$ (920,983)	$ 0	$ (160)	$ 160
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)	0	(160)	160
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
Net proceeds from 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
Cumulative-effect adjustment from adoption of ASU 2018-07	11,301	$ 3,906	$ 0	$ 3	959,900	(952,508)	0	(160)	160
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)
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)	0	(160)	160
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(62,101)
Cumulative-effect adjustment from adoption of ASU 2018-07	(12,593)	$ 3,906	$ 0	$ 3	966,422	(982,924)	$ 0	$ (160)	$ 160
Ending Balance (in shares) at Jun. 30, 2019		4,000	0	27,125,000
Ending Balance at Jun. 30, 2019	(12,593)	$ 3,906	$ 0	$ 3	966,422	(982,924)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	11,301	$ 3,906	$ 0	$ 3	959,900	(952,508)
Beginning Balance (in shares) at Mar. 31, 2019		4,000	0	27,093,000
Beginning Balance at Mar. 31, 2019	11,301	$ 3,906	$ 0	$ 3	959,900	(952,508)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	6,321
Issuance of common stock under ESPP (in shares)				32,000
Net proceeds from issuance of common stock under ESPP	201				201
Net loss	(30,416)					(30,416)
Cumulative-effect adjustment from adoption of ASU 2018-07	(12,593)	$ 3,906	$ 0	$ 3	966,422	(982,924)
Ending Balance (in shares) at Jun. 30, 2019		4,000	0	27,125,000
Ending Balance at Jun. 30, 2019	(12,593)	$ 3,906	$ 0	$ 3	966,422	(982,924)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	(12,593)	3,906	0	3	966,422	(982,924)
Cumulative-effect adjustment from adoption of ASU 2018-07	(55,990)	$ 3,906	$ 0	$ 3	977,432	(1,037,331)
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)				44,000
Net proceeds from issuance of common stock under 2013 Equity Plan	305				305
Issuance of common stock under ESPP (in shares)				38,000
Net proceeds from issuance of common stock under ESPP	200				200
Net loss	(8,591)					(8,591)
Cumulative-effect adjustment from adoption of ASU 2018-07	(61,669)	$ 3,906	$ 0	$ 3	980,344	(1,045,922)
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)
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	$ 3,997
Exercise of stock options for common stock (in shares)	94,219
Net loss	$ (24,183)
Cumulative-effect adjustment from adoption of ASU 2018-07	(75,212)	$ 3,906	$ 0	$ 3	982,393	(1,061,514)
Ending Balance (in shares) at Jun. 30, 2020		4,000	0	27,359,000
Ending Balance at Jun. 30, 2020	(75,212)	$ 3,906	$ 0	$ 3	982,393	(1,061,514)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	(61,669)	$ 3,906	$ 0	$ 3	980,344	(1,045,922)
Beginning Balance (in shares) at Mar. 31, 2020		4,000	0	27,277,000
Beginning Balance at Mar. 31, 2020	(61,669)	$ 3,906	$ 0	$ 3	980,344	(1,045,922)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,590				1,590
Exercise of stock options for common stock (in shares)				50,000
Net proceeds from issuance of common stock under 2013 Equity Plan	300				300
Issuance of common stock under ESPP (in shares)				32,000
Net proceeds from issuance of common stock under ESPP	159				159
Net loss	(15,592)					(15,592)
Cumulative-effect adjustment from adoption of ASU 2018-07	(75,212)	$ 3,906	$ 0	$ 3	982,393	(1,061,514)
Ending Balance (in shares) at Jun. 30, 2020		4,000	0	27,359,000
Ending Balance at Jun. 30, 2020	(75,212)	$ 3,906	$ 0	$ 3	982,393	(1,061,514)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2018-07	$ (75,212)	$ 3,906	$ 0	$ 3	$ 982,393	$ (1,061,514)