Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities
Net loss	$ (61,777,000)	$ (144,796,000)	$ (119,980,000)
Adjustments to reconcile net loss to net cash and cash equivalents used in operating activities:
Gain from sale of SurgiBot assets, net	(11,840,000)
Depreciation	2,420,000	2,486,000	1,942,000
Amortization of intangible assets	10,868,000	7,858,000	6,967,000
Amortization of debt discount and debt issuance costs	725,000	510,000	177,000
Amortization of short-term investment discount	(351,000)
Stock-based compensation	9,039,000	7,078,000	5,033,000
Non-employee warrant awards		838,000
Common stock issued for services			116,000
Inventory write-down related to restructuring			2,565,000
Non-cash restructuring and other charges			2,556,000
Goodwill impairment	0	0	61,784,000
Deferred tax benefit	(3,377,000)	(3,300,000)	(5,562,000)
Loss on extinguishment of debt	1,400,000	308,000
Change in fair value of warrant liabilities	14,320,000	83,734,000
Change in fair value of contingent consideration	(1,011,000)	2,026,000	482,000
Reversal of transfer fee accrual	(2,994,000)
Changes in operating assets and liabilities, net of effect of acquisition:
Accounts receivable	(7,225,000)	(381,000)	(1,041,000)
Interest receivable	54,000	23,000	(6,000)
Inventories	(2,145,000)	(2,981,000)	(6,647,000)
Other current and long term assets	(325,000)	(3,348,000)	(1,528,000)
Accounts payable	767,000	(531,000)	(356,000)
Accrued expenses	2,134,000	2,093,000	1,112,000
Deferred revenue	825,000	1,088,000
Net cash and cash equivalents used in operating activities	(48,493,000)	(47,295,000)	(52,386,000)
Investing Activities
Purchase of short-term investments	(55,439,000)
Proceeds from maturities of short-term investments	4,000,000
Payment for acquisition of a business	(5,800,000)
Proceeds related to sale of SurgiBot assets, net	4,496,000	7,500,000
Purchase of property and equipment	(770,000)	(1,566,000)	(1,361,000)
Purchase of intellectual property		(425,000)
Proceeds from sale of property and equipment	32,000
Net cash and cash equivalents (used in) provided by investing activities	(53,481,000)	5,509,000	(1,361,000)
Financing Activities
Payment of notes payable	(15,305,000)	(13,343,000)	(6,902,000)
Proceeds from issuance of debt and warrants, net of issuance costs	28,507,000	13,005,000
Payment of contingent consideration	(770,000)	(7,181,000)	(1,182,000)
Proceeds from issuance of common stock and warrants, net of issuance costs	279,000	77,579,000	58,029,000
Taxes paid related to net share settlement of vesting of restricted stock units	(1,662,000)	(168,000)	(168,000)
Proceeds from issuance of common stock related to sale of SurgiBot assets	3,000,000
Proceeds from exercise of stock options and warrants	12,403,000	34,479,000	166,000
Net cash and cash equivalents provided by financing activities	26,452,000	104,371,000	49,943,000
Effect of exchange rate changes on cash and cash equivalents	(433,000)	431,000	(55,000)
Net (decrease) increase in cash, cash equivalents and restricted cash	(75,955,000)	63,016,000	(3,859,000)
Cash, cash equivalents and restricted cash, beginning of period	97,606,000	34,590,000	38,449,000
Cash, cash equivalents and restricted cash, end of period	21,651,000	97,606,000	34,590,000
Supplemental Disclosure for Cash Flow Information
Interest paid	1,730,000	899,000	1,289,000
Supplemental Schedule of Noncash Investing and Financing Activities
Transfer of inventories to property and equipment	2,160,000	1,258,000	$ 3,198,000
Transfer of property and equipment to inventories	637,000
Issuance of common stock as contingent consideration		5,227,000
Relative fair value of warrants issued with debt		300,000
Reclass of warrant liability to common stock and additional paid in capital	23,774,000	78,359,000
Transfer of in-process research and development to intellectual property		17,913,000
Cashless exercise of warrants	4,272,000	$ 149,000
Issuance of common stock related to acquisition	8,300,000
Deferred consideration - MST acquistion	$ 5,962,000