CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net loss	$ (12,974)	$ (22,636)
Adjustments to reconcile net loss to net cash provided by (used for) operating activities:
Depreciation and amortization expense	1,079	698
Stock compensation expense	8,144	6,810
Foreign currency translation loss	45	13
Loss on sale of fixed assets	30	0
Amortization of premiums and discounts on marketable securities	(25)	(408)
Amortization and interest accretion related to operating leases	1,603	1,139
Changes in operating assets and liabilities:
Inventory	(1,601)	(1,230)
Accounts receivable	8,513	2,370
Prepaid and other current assets	53	680
Accounts payable	(1,692)	(2,238)
Accrued expenses	27	(2,229)
Operating lease liabilities	(1,537)	(1,007)
Other non-current assets and liabilities, net	0	(187)
Net cash provided by (used for) operating activities	1,665	(18,225)
Investing activities:
Purchases of short term investments	(5,657)	(32,402)
Maturities of short term investments	32,797	45,477
Expenditures for property, plant and equipment	(1,186)	(1,224)
Net cash provided by investing activities	25,954	11,851
Financing activities:
Net proceeds from common stock issuance due to stock option exercises	1,373	2,059
Payments on employee's behalf for taxes related to vesting of restricted stock unit awards	(163)	0
Other	(14)	(9)
Net cash provided by financing activities	1,196	2,050
Net increase in cash, cash equivalents, and restricted cash	28,815	(4,324)
Cash, cash equivalents, and restricted cash at beginning of period	26,978	18,286
Cash, cash equivalents, and restricted cash at end of period	$ 55,793	$ 13,962