CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net loss	$ (36,206)	$ (15,307)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	3,402	3,637
Stock-based compensation	15,501	11,813
Accretion of discount or amortization of premium on short-term investments	85	(464)
Amortization of debt issuance costs and debt discount	2,719	51
Changes in operating assets and liabilities:
Accounts receivable	6,005	(6,341)
Inventory	(3,829)	8,451
Prepaid expenses and other assets	(1,637)	(222)
Deferred revenue	449	114
Accounts payable	2,608	1,508
Accrued compensation and employee related benefits	(1,797)	(2,440)
Operating lease right-of-use assets	2,029	1,505
Operating lease liabilities	(2,509)	(2,255)
Accrued liabilities and other liabilities	(372)	164
Net cash provided by (used in) operating activities	(13,552)	214
Investing activities:
Purchases of investments	(57,298)	(59,036)
Proceeds from maturities of investments	41,675	51,794
Purchases of property and equipment	(2,336)	(971)
Net cash used in investing activities	(17,959)	(8,213)
Financing activities:
Principal payments on finance lease obligations	(240)	(410)
Payments on term and equipment loans		(4,222)
Proceeds from term loans, net of debt issuance costs		3,991
Proceeds from exercise of stock options and employee stock purchase plan	4,916	8,041
Net cash provided by financing activities	4,676	7,400
Net decrease in cash and cash equivalents	(26,835)	(599)
Cash and cash equivalents
Beginning of period	66,898	17,530
End of period	40,063	16,931
Supplemental disclosure of cashflow information:
Cash paid for interest	858	1,179
Purchases of property and equipment not yet paid	$ 544	$ 105