Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive (Loss) Income [Member]
Balance at Dec. 31, 2015	$ 177,277	$ 100	$ (73)	$ 363,280	$ (182,864)	$ (3,166)
Balance, Shares at Dec. 31, 2015		100,180	(31)
Stock-based compensation	5,033			5,033
Issuance of common stock, net of issuance costs	58,029	$ 15		58,014
Issuance of common stock, net of issuance costs, Shares		15,086
Exercise of stock options and restricted stock units	166			166
Exercise of stock options and restricted stock units, Shares		419
Return of common stock to pay withholding taxes on restricted stock	(168)		$ (168)
Return of common stock to pay withholding taxes on restricted stock, Shares			(63)
Issuance of common stock for services	116			116
Issuance of common stock for services, Shares		96
Other comprehensive loss	(2,603)					(2,603)
Net loss	(119,980)				(119,980)
Balance at Dec. 31, 2016	117,870	$ 115	$ (241)	426,609	(302,844)	(5,769)
Balance, Shares at Dec. 31, 2016		115,781	(94)
Stock-based compensation	7,078			7,078
Non-employee warrant awards	838			838
Issuance of common stock and treasury stock, net of issuance costs	68,864	$ 45	$ 409	68,410
Issuance of common stock and treasury stock, net of issuance costs, Shares		44,689	213
Exercise of stock options and warrants	112,838	$ 35		112,803
Exercise of stock options and warrants, Shares		34,749
Award of restricted stock units, Shares		340
Return of common stock to pay withholding taxes on restricted stock	(168)		$ (168)
Return of common stock to pay withholding taxes on restricted stock, Shares			(119)
Issuance of common stock in exchange for contingent consideration	5,227	$ 4		5,223
Issuance of common stock in exchange for contingent consideration, Shares		3,723
Relative fair value of warrants issued with debt	300			300
Other comprehensive loss	10,797					10,797
Net loss	(144,796)				(144,796)
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	9,039			9,039
Issuance of common stock and warrants, net of issuance costs	279			279
Issuance of common stock for MST Acquisition	8,300	$ 3		8,297
Issuance of common stock for MST acquisition, Shares		3,150
Exercise of stock options and warrants	36,173	$ 12		36,161
Exercise of stock options and warrants, Shares		11,559
Award of restricted stock units	1	$ 1
Award of restricted stock units, Shares		1,069
Return of common stock to pay withholding taxes on restricted stock	(1,662)		$ 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	(3,690)					(3,690)
Net loss	(61,777)				(61,777)
Balance at Dec. 31, 2018	$ 168,521	$ 216		$ 676,373	$ (509,406)	$ 1,338
Balance, Shares at Dec. 31, 2018		216,346