UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 9,165	$ 8,880	$ 20,935	$ 28,296
Costs and expenses:
Operating expenses (excluding depreciation and amortization)	12,110	11,632	25,911	34,473
Corporate general and administrative	2,868	5,395	7,229	9,888
Depreciation and amortization	253	468	560	2,659
Research and development	1,466	1,638	3,008	4,193
Gain on disposal of long-lived assets	(71)	(22)	(69)	(55)
Impairment of fixed, long-lived and intangible assets	0	0	0	57,454
Total costs and expenses	16,626	19,111	36,639	108,612
Loss from operations	(7,461)	(10,231)	(15,704)	(80,316)
Other (expense) income:
Payment Protection Program forgiveness	881	0	881	0
Gain on lease termination	0	576	0	576
Interest expense	(17)	(16)	(35)	(20)
Other income, net	72	78	39	31
Total other income, net	936	638	885	587
Loss before income taxes	(6,525)	(9,593)	(14,819)	(79,729)
Income tax (expense) benefit	(21)	32	(27)	6,201
Net loss	$ (6,546)	$ (9,561)	$ (14,846)	$ (73,528)
Loss per common share:
Basic (in dollars per share)	$ (0.09)	$ (0.14)	$ (0.22)	$ (1.17)
Diluted (in dollars per share)	$ (0.09)	$ (0.14)	$ (0.22)	$ (1.17)
Weighted average common shares:
Weighted average common shares used in computing basic loss per common share (in shares)	69,531	66,035	69,001	62,828
Weighted average common shares used in computing diluted loss per common share (in shares)	69,531	66,035	69,001	62,828