CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net loss	$ (4,705)	$ (2,844)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	533	324
Stock compensation expense	3,768	2,628
Foreign currency translation loss	7	6
Amortization of premiums and discounts on marketable securities	(20)	(215)
Amortization and interest accretion related to operating leases	794	387
Changes in operating assets and liabilities:
Inventory	(466)	(505)
Accounts receivable	7,997	4,680
Prepaid and other current assets	(549)	168
Accounts payable	(59)	(1,368)
Accrued expenses	(1,864)	(2,751)
Operating lease liabilities	(750)	(310)
Other non-current assets and liabilities, net	0	(46)
Net cash provided by operating activities	4,686	154
Investing activities:
Purchases of short term investments	(5,676)	(10,686)
Maturities of short term investments	20,135	26,580
Expenditures for property, plant and equipment	(717)	(232)
Net cash provided by investing activities	13,742	15,662
Financing activities:
Net proceeds from common stock issuance due to stock option exercises	420	998
Payments on employee's behalf for taxes related to vesting of restricted stock unit awards	(97)	0
Other	(17)	(16)
Net cash provided by financing activities	306	982
Net increase in cash, cash equivalents, and restricted cash	18,734	16,798
Cash, cash equivalents, and restricted cash at beginning of period	26,978	18,286
Cash, cash equivalents, and restricted cash at end of period	$ 45,712	$ 35,084