Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Operating Activities
Net loss			$ (42,696)	$ (35,130)
Adjustments to reconcile net loss to net cash and cash equivalents used in operating activities:
Loss (gain) from sale of SurgiBot assets, net	$ 0	$ 37	97	(11,959)
Depreciation			1,126	1,277
Amortization of intangible assets	2,585	2,743	5,196	5,570
Amortization of debt discount and debt issuance costs			622	495
Amortization of short-term investment discount			(300)	0
Interest expense on deferred consideration - MST acquisition			387	0
Stock-based compensation			6,336	4,204
Deferred tax benefit			(1,479)	(1,799)
Write down of inventory			761	0
Change in fair value of warrant liabilities	(2,528)	17,507	(2,422)	15,678
Change in fair value of contingent consideration	960	812	1,958	1,439
Loss on extinguishment of debt			0	1,400
Changes in operating assets and liabilities:
Accounts receivable			2,808	(762)
Interest receivable			(4)	(24)
Inventories			(10,301)	(1,560)
Other current and long term assets			(3,689)	1,905
Accounts payable			2,499	404
Accrued expenses			(1,454)	(359)
Deferred revenue			(862)	31
Other long term liabilities			1,879	0
Net cash and cash equivalents used in operating activities			(39,538)	(19,190)
Investing Activities
Purchase of short-term investments			(12,883)	0
Proceeds from maturities of short-term investments			55,000	0
Proceeds related to sale of SurgiBot assets, net			0	4,496
Purchase of property and equipment			(189)	(358)
Proceeds from sale of property and equipment			0	32
Net cash and cash equivalents provided by investing activities			41,928	4,170
Financing Activities
Payment of note payable			0	(15,305)
Proceeds from issuance of debt and warrants, net of issuance costs			(30)	18,870
Payment of contingent consideration			0	(395)
Proceeds from issuance of common stock and warrants, net of issuance costs			0	2
Taxes paid related to net share settlement of vesting of restricted stock units			(499)	0
Proceeds from issuance of common stock related to sale of SurgiBot assets			0	3,000
Proceeds from exercise of stock options and warrants			534	9,813
Net cash and cash equivalents provided by financing activities			5	15,985
Effect of exchange rate changes on cash and cash equivalents			(32)	(78)
Net increase in cash, cash equivalents and restricted cash			2,363	887
Cash, cash equivalents and restricted cash, beginning of period			21,651	97,606	$ 97,606
Cash, cash equivalents and restricted cash, end of period	$ 24,014	$ 98,493	24,014	98,493	$ 21,651
Supplemental Disclosure for Cash Flow Information
Interest paid			1,528	599
Supplemental Schedule of Noncash Investing and Financing Activities
Transfer of inventories to property and equipment			415	1,055
Reclass of warrant liability to common stock and additional paid-in capital			$ 0	$ 7,060