Condensed Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (80,731)	$ (60,233)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	12,420	9,789
Depreciation and amortization	2,586	2,553
Non-cash lease expense	544	501
Non-cash interest expense	282	282
Accretion of discount on investments, net	1,035	435
Provision for inventories	808	325
Other non-cash items	29	5
Changes in operating assets and liabilities:
Accounts receivable	964	(9,946)
Inventories	(15,311)	(12,116)
Prepaid expenses and other assets	70	570
Accounts payable	684	(2,509)
Accrued payroll and related benefits	(9,153)	(1,538)
Accrued expenses and other current liabilities	8,366	1,508
Accrued warranty liability	(260)	160
Deferred revenue	1,305	1,117
Operating lease liabilities	(548)	(360)
Net cash used in operating activities	(76,910)	(69,457)
Cash flows from investing activities:
Purchases of property and equipment	(3,475)	(1,766)
Purchases of investment securities	(133,015)	(122,401)
Sales and maturities of investment securities	101,784	19,900
Net cash used in investing activities	(34,706)	(104,267)
Cash flows from financing activities:
Proceeds from stock option exercises and employee stock purchase plan purchases	4,765	3,941
Proceeds from issuance of common stock upon follow-on public offering, net of issuance costs	0	149,085
Net cash provided by financing activities	4,765	153,026
Net decrease in cash, cash equivalents and restricted cash	(106,851)	(20,698)
Cash, cash equivalents and restricted cash as of beginning of period	215,659	328,283
Cash, cash equivalents and restricted cash as of end of period	108,808	307,585
Supplemental cash flow disclosures:
Cash paid for income taxes	283	42
Cash paid for interest	621	149
Cash paid for amounts included in the measurement of operating lease liabilities	548	360
Supplemental non-cash investing and financing activities:
Capital expenditures included in accounts payable and accrued expenses	1,613	92
Transfer of inventories to property and equipment	$ 0	$ 1,294