Consolidated Statements of Shareholders' Equity - 6 months ended Jun. 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	4,204			4,204
Issuance of common stock and warrants, net of issuance costs	2			2
Exercise of stock options and warrants	16,873	$ 7		16,866
Exercise of stock options and warrants, Shares		6,773
Award of restricted stock units		371
Return of common stock to pay withholding taxes on restricted stock, Shares			176
Cancellation of treasury stock, Shares			(176)
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	(2,090)					(2,090)
Net loss	(35,130)				(35,130)
Balance at Jun. 30, 2018	$ 165,718	$ 207		$ 645,332	$ (482,759)	$ 2,938
Balance, Shares at Jun. 30, 2018		207,712