CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (17,776)	$ (22,097)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	993	631
Amortization of right-of-use assets	1,282	1,352
Amortization of intangible assets	111	89
Amortization of deferred financing fees	22
Provision for bad debt	(115)	(150)
Provision for inventory write-down	2,108	(44)
Changes in fair value of derivatives	71
Changes in investment gains and losses	(29)	(957)
Share-based compensation	5,725	7,384
Change in operating assets and liabilities:
Accounts receivable	(1,700)	20
Inventory	(176)	(1,657)
Prepaid expenses and other	(844)	(1,099)
Accounts payable and accrued expenses	(911)	1,288
Operating lease obligations	(1,213)	(1,276)
Cash paid for interest portion of finance leases	(2)	(3)
Contract and other liabilities	(9)	(23)
Net cash used in operating activities	(12,463)	(16,542)
Cash flows from investing activities:
Purchase of property and equipment	(18,907)	(3,676)
Purchase of investments	(41,794)	(104,314)
Proceeds from sale of investments	63,483	122,071
Cash payments for intangible assets	(393)	(396)
Net cash provided by investing activities	2,389	13,685
Cash flows from financing activities:
Proceeds from the issuance of long-term debt	35,000
Proceeds from the paycheck protection program	7,820
Repayment of paycheck protection program	(7,820)
Payments for debt issuance costs	(642)
Payments of employee tax withholding in exchange of common stock awards	(665)
Cash paid for debt portion of finance leases	(10)	(24)
Proceeds from exercise of stock options	2,276	3,142
Net cash provided by financing activities	35,959	3,118
Net increase in cash, cash equivalents, and restricted cash	25,885	261
Cash, cash equivalents, and restricted cash, beginning of period	41,724	30,294
Cash, cash equivalents and restricted cash, end of period	67,609	30,555
Supplemental disclosures of cash flow activity:
Cash paid for interest	379	31
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of fixed assets in accounts payable and accrued expenses	1,271	684
Obtaining a right-of-use asset in exchange for a lease liability	14,119	$ 26
Embedded derivative associated with the long-term debt	$ 2,562