CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net loss	$ (3,289)	$ (4,705)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense	811	533
Stock compensation expense	7,019	3,768
Foreign currency translation loss	2	7
Gain on sale of fixed assets	(22)	0
Amortization of premiums and discounts on marketable securities	273	(20)
Non-cash lease cost	1,171	794
Changes in operating assets and liabilities:
Inventory	(966)	(466)
Accounts receivable	5,382	7,997
Other current assets	(320)	(549)
Accounts payable	2,174	(59)
Accrued expenses	(1,328)	(1,864)
Operating lease liabilities	(821)	(750)
Net cash provided by operating activities	10,086	4,686
Investing activities:
Purchases of investments	(10,426)	(5,676)
Sales and maturities of investments	24,955	20,135
Expenditures for property, plant and equipment	(2,343)	(717)
Net cash provided by investing activities	12,186	13,742
Financing activities:
Net proceeds from common stock issuance due to stock option exercises	3,781	420
Payments on employee's behalf for taxes related to vesting of restricted stock units	(1,501)	(97)
Other	(18)	(17)
Net cash provided by financing activities	2,262	306
Net increase in cash, cash equivalents, and restricted cash	24,534	18,734
Cash, cash equivalents, and restricted cash at beginning of period	33,831	26,978
Cash, cash equivalents, and restricted cash at end of period	$ 58,365	$ 45,712