Consolidated Statements of Shareholders' Equity - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Balance at Dec. 31, 2017	$ 178,848	$ 199		$ 621,261	$ (447,640)	$ 5,028
Balance, Shares at Dec. 31, 2017		199,282
Stock-based compensation	6,694			6,694
Issuance of common stock and warrants, net of issuance costs	279			279
Exercise of stock options and warrants	34,880	$ 11		34,869
Exercise of stock options and warrants, Shares		11,028
Award of restricted stock units	1	$ 1
Award of restricted stock units, Shares		1,036
Return of common stock to pay withholding taxes on restricted stock	(1,664)		$ (1)	(1,663)
Return of common stock to pay withholding taxes on restricted stock, Shares			(537)
Cancellation of treasury stock	1		$ 1
Cancellation of treasury stock, Shares			537
Issuance of common stock related to sale of SurgiBot assets	3,000	$ 1		2,999
Issuance of common stock related to sale of SurgiBot assets, Shares		1,286
Cumulative effect of change in accounting principle (Note 2)	11				11
Other comprehensive loss	(2,651)					(2,651)
Net loss	(55,336)				(55,336)
Balance at Sep. 30, 2018	$ 164,063	$ 212		$ 664,439	$ (502,965)	$ 2,377
Balance, Shares at Sep. 30, 2018		212,632