Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities
Net loss	$ (55,336)	$ (68,640)
Adjustments to reconcile net loss to net cash and cash equivalents used in operating activities:
Gain from sale of SurgiBot assets, net	(11,915)
Depreciation	1,876	1,816
Amortization of intangible assets	8,244	5,144
Amortization of debt discount and debt issuance costs	575	212
Amortization of held to maturity investment discount	(51)
Stock-based compensation	6,694	5,321
Non-employee warrant awards		571
Deferred tax benefit	(2,572)	(2,320)
Loss on extinguishment of debt	1,400	308
Change in fair value of warrant liabilities	24,438	25,213
Change in fair value of contingent consideration	81	1,226
Recovery of transfer fee	(2,994)
Changes in operating assets and liabilities:
Accounts receivable	(4,262)	886
Interest receivable	28	79
Inventories	(1,276)	(3,519)
Other current and long term assets	27	(2,454)
Accounts payable	(903)	(1,599)
Accrued expenses	(56)	207
Deferred revenue	361
Net cash and cash equivalents used in operating activities	(35,641)	(37,549)
Investing Activities
Purchase of short-term investments	(39,619)
Proceeds related to sale of SurgiBot assets, net	4,496
Purchase of property and equipment	(490)	(1,488)
Purchase of intellectual property		(418)
Proceeds from sale of property and equipment	32
Net cash and cash equivalents used in investing activities	(35,581)	(1,906)
Financing Activities
Payment of notes payable	(15,305)	(13,343)
Proceeds from issuance of debt and warrants, net of issuance costs	18,828	12,956
Payment of contingent consideration	(395)	(395)
Proceeds from issuance of common stock and warrants, net of issuance costs	279	31,546
Taxes paid related to net share settlement of vesting of restricted stock units	(1,662)	(168)
Proceeds from issuance of common stock related to sale of SurgiBot assets	3,000
Proceeds from exercise of stock options and warrants	11,396	5,449
Net cash and cash equivalents provided by financing activities	16,141	36,045
Effect of exchange rate changes on cash and cash equivalents	(114)	(311)
Net decrease in cash, cash equivalents and restricted cash	(55,195)	(3,721)
Cash, cash equivalents and restricted cash, beginning of period	97,606	34,590
Cash, cash equivalents and restricted cash, end of period	42,411	30,869
Supplemental Disclosure for Cash Flow Information
Interest paid	1,135	597
Supplemental Schedule of Noncash Investing and Financing Activities
Transfer of inventories to property and equipment	2,160
Transfer of property and equipment to inventories	648
Issuance of common stock as contingent consideration		5,227
Relative fair value of warrants issued with debt		300
Reclass of warrant liability to common stock and additional paid-in capital	23,485	$ 2,289
Cashless exercise of warrants	$ 4,272