CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' DEFICIT - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss)	Total
Balance beginning at Dec. 31, 2018	$ 192,000	$ 1,144,621,000	$ (1,299,107,000)	$ (2,450,000)	$ (11,191,000)	$ (167,935,000)
Balance beginning (in shares) at Dec. 31, 2018	19,245,302
Non-cash compensation cost for stock options, RSUs, SARs and ESPP	$ 0	5,558,000	0	0	0	5,558,000
Exercise of stock options/Purchases under ESPP	$ 1,000	941,000	0	0	0	942,000
Exercise of stock options/Purchases under ESPP, (in shares)	51,388
Issuance of common stock, net of issuance costs	$ 42,000	55,197,000	0	0	0	55,239,000
Issuance of common stock, net of issuance costs, (in shares)	4,198,776
Unrealized gain on marketable securities	$ 0	0	0	0	5,000	5,000
Foreign currency translation adjustment	0	0	0	0	(1,174,000)	(1,174,000)
Net loss	0	0	(43,218,000)	0	0	(43,218,000)
Balance ending at Mar. 31, 2019	$ 235,000	1,206,317,000	(1,342,325,000)	(2,450,000)	(12,360,000)	(150,583,000)
Balance ending (in shares) at Mar. 31, 2019	23,495,466
Balance beginning at Dec. 31, 2019	$ 324,000	1,260,551,000	(1,431,801,000)	(2,583,000)	(12,508,000)	(186,017,000)
Balance beginning (in shares) at Dec. 31, 2019	32,399,352
Non-cash compensation cost for stock options, RSUs, SARs and ESPP	$ 0	3,965,000	0	0	0	3,965,000
Vesting of RSUs/Purchases under ESPP	$ 0	60,000	0	(55,000)	0	5,000
Vesting of RSUs/Purchases under ESPP (in shares)	33,239
Issuance of common stock, net of issuance costs	$ 215,000	185,703,000	0	0	0	185,918,000
Issuance of common stock, net of issuance costs, (in shares)	21,473,731
Unrealized gain on marketable securities	$ 0	0	0	0	(132,000)	(132,000)
Foreign currency translation adjustment	0	0	0	0	(1,846,000)	(1,846,000)
Net loss	0	0	(25,864,000)	0	0	(25,864,000)
Balance ending at Mar. 31, 2020	$ 539,000	$ 1,450,279,000	$ (1,457,665,000)	$ (2,638,000)	$ (14,486,000)	$ (23,971,000)
Balance ending (in shares) at Mar. 31, 2020	53,906,322