Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows from Operating Activities
Net loss	$ (34,399)	$ (32,178)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	806	570
Stock-based compensation	7,738	3,017
Amortization of debt issuance costs	414	434
Provision for doubtful accounts	514	0
Other items, net	81	0
Changes in operating assets and liabilities
Accounts receivable	(6,750)	(859)
Inventory	(14,427)	(4,302)
Prepaid expenses and other current assets	975	891
Other assets	116	(5)
Accounts payable	4,846	(881)
Accrued liabilities	1,574	1,027
Accrued compensation and benefits	1,914	920
Lease liability	316	(48)
Net cash used in operating activities	(36,282)	(31,414)
Cash Flows from Investing Activities
Purchases of property and equipment	(1,267)	(729)
Purchases of short-term investments	0	(33,231)
Proceeds from sales and maturities of short-term investments	12,592	49,449
Net cash provided by investing activities	11,325	15,489
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	1,352	352
Net cash provided by financing activities	141,839	352
Effect of exchange rate changes on cash and cash equivalents	(285)	(53)
Net increase (decrease) in cash and cash equivalents	116,597	(15,626)
Cash and cash equivalents, beginning of year	171,082	98,306
Cash and cash equivalents, end of period	287,679	82,680
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	593	730
Cash paid for taxes	$ 0	$ 1