CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net income (loss)	$ (9,356)	$ (19,166)
Adjustments to reconcile net loss to net cash provided by (used for) operating activities:
Depreciation and amortization expense	1,649	1,174
Stock compensation expense	10,819	10,095
Foreign currency translation loss	59	21
Loss on sale of fixed assets	30	0
Amortization of premiums and discounts on marketable securities	24	(529)
Amortization and interest accretion related to operating leases	3,312	2,011
Changes in operating assets and liabilities:
Inventory	(3,264)	(3,265)
Accounts receivable	5,994	3,496
Other current assets	(633)	(425)
Accounts payable	(52)	(1,895)
Accrued expenses	747	30
Operating lease liabilities	(3,110)	(1,804)
Other non-current assets and liabilities, net	16	(76)
Net cash provided by (used for) operating activities	6,235	(10,333)
Investing activities:
Purchases of short-term investments	(29,049)	(46,303)
Maturities of short-term investments	39,123	73,777
Expenditures for property, plant and equipment	(1,556)	(2,255)
Net cash provided by investing activities	8,518	25,219
Financing activities:
Net proceeds from common stock issuance due to stock option exercises	2,182	3,762
Payments on employee's behalf for taxes related to vesting of restricted stock unit awards	(163)	0
Other	(32)	(29)
Net cash provided by financing activities	1,987	3,733
Net increase in cash, cash equivalents, and restricted cash	16,740	18,619
Cash, cash equivalents, and restricted cash at beginning of period	26,978	18,286
Cash, cash equivalents, and restricted cash at end of period	$ 43,718	$ 36,905