CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Treasury Stock [Member]	Other Comprehensive Income (Loss)
Balance beginning at Dec. 31, 2017	$ (101,732)	$ 3,237	$ 1,020,457	$ (1,114,359)	$ (2,450)	$ (8,617)
Balance beginning (in shares) at Dec. 31, 2017		323,684,820
Non-cash compensation cost for stock options,RSUs, ESPP and restricted stock	5,245	$ 0	5,245	0	0	0
Exercise of stock options/Purchases under ESPP	1,325	$ 11	1,314	0	0	0
Exercise of stock options/Purchases under ESPP, shares		1,108,210
Restricted stock cancelled	0	$ 0	0	0	0	0
Restricted stock cancelled, in shares		(18,750)
Issuance of common stock, net of issuance costs	42,599	$ 224	42,375	0	0	0
Issuance of common stock, net of issuance costs, in shares		22,430,136
Unrealized gain on marketable securities	8	$ 0	0	0	0	8
Foreign currency translation adjustment	(462)	0	0	0	0	(462)
Net loss	(46,352)	0	0	(46,352)	0	0
Balance ending at Mar. 31, 2018	(99,369)	$ 3,472	1,069,391	(1,160,711)	(2,450)	(9,071)
Balance ending (in shares) at Mar. 31, 2018		347,204,416
Balance beginning at Dec. 31, 2017	(101,732)	$ 3,237	1,020,457	(1,114,359)	(2,450)	(8,617)
Balance beginning (in shares) at Dec. 31, 2017		323,684,820
Balance ending at Dec. 31, 2018	(167,935)	$ 3,849	1,140,964	(1,299,107)	(2,450)	(11,191)
Balance ending (in shares) at Dec. 31, 2018		384,906,037
Non-cash compensation cost for stock options,RSUs, ESPP and restricted stock	5,558	$ 0	5,558	0	0	0
Exercise of stock options/Purchases under ESPP	942	$ 10	932	0	0	0
Exercise of stock options/Purchases under ESPP, shares		1,027,753
Issuance of common stock, net of issuance costs	55,239	$ 840	54,399	0	0	0
Issuance of common stock, net of issuance costs, in shares		83,975,523
Unrealized gain on marketable securities	5	$ 0	0	0	0	5
Foreign currency translation adjustment	(1,174)	0	0	0	0	(1,174)
Net loss	(43,218)	0	0	(43,218)	0	0
Balance ending at Mar. 31, 2019	$ (150,583)	$ 4,699	$ 1,201,853	$ (1,342,325)	$ (2,450)	$ (12,360)
Balance ending (in shares) at Mar. 31, 2019		469,909,313