Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows from Operating Activities
Net loss	$ (43,567)	$ (57,184)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	1,253	880
Stock-based compensation	11,513	5,799
Amortization of debt issuance costs	594	659
Provision for doubtful accounts	390	0
Other items, net	142	0
Changes in operating assets and liabilities
Accounts receivable	(10,161)	(527)
Inventory	(28,600)	(9,030)
Prepaid expenses and other current assets	1,352	1,091
Other assets	16	(327)
Accounts payable	3,533	796
Accrued liabilities	3,508	532
Accrued compensation and benefits	4,141	2,089
Lease liability	458	(96)
Net cash used in operating activities	(55,428)	(55,318)
Cash Flows from Investing Activities
Purchases of property and equipment	(1,915)	(962)
Purchases of short-term investments	0	(35,210)
Proceeds from sales and maturities of short-term investments	12,592	69,117
Net cash provided by investing activities	10,677	32,945
Cash Flows from Financing Activities
Proceeds from issuance of common stock upon follow-on public offering	149,500	0
Payment of common stock issuance costs upon follow-on public offering	(9,013)	0
Proceeds from exercise of stock options	2,648	463
Net cash provided by financing activities	143,135	463
Effect of exchange rate changes on cash and cash equivalents	(186)	(165)
Net increase (decrease) in cash and cash equivalents	98,198	(22,075)
Cash and cash equivalents, beginning of year	171,082	98,306
Cash and cash equivalents, end of period	269,280	76,231
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	849	1,097
Cash paid for taxes	$ 0	$ 1