CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net loss	$ (9,416)	$ (4,326)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation	1,040	1,168
Stock-based compensation	7,449	5,221
Accretion of discount or amortization of premium on short-term investments	218	(4)
Amortization of debt issuance costs and debt discount	94	879
Changes in operating assets and liabilities:
Accounts receivable	1,498	(4,371)
Inventory	8,262	2,390
Prepaid expenses and other assets	880	368
Deferred revenue	(633)	155
Accounts payable	(2,137)	1,096
Accrued compensation and employee related benefits	345	(1,933)
Operating lease right-of-use assets	723	657
Operating lease liabilities	(911)	(823)
Accrued and other liabilities	722	1,368
Restructuring liabilities	1,235
Net cash provided by operating activities	9,369	1,845
Investing activities:
Purchases of investments	(12,333)
Proceeds from maturities of investments	25,000	14,175
Purchases of property and equipment	(4,398)	(1,112)
Net cash provided by investing activities	8,269	13,063
Financing activities:
Principal payments on finance lease obligations	(2)	(98)
Proceeds from exercise of stock options and employee stock purchase plan	8,524	2,014
Net cash provided by financing activities	8,522	1,916
Net increase in cash and cash equivalents	26,160	16,824
Cash and cash equivalents
Beginning of period	23,636	66,898
End of period	49,796	83,722
Supplemental disclosure of cashflow information:
Purchases of property and equipment not yet paid	$ 1,984	$ 94