Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net Income (Loss)	$ (172,797)	$ (162,956)	$ (131,935)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	38,634	27,203	17,445
Depreciation and amortization	5,810	5,169	5,162
Non-cash lease expense	1,271	1,114	1,022
Non-cash interest expense	1,828	381	569
Accretion of discount on investments, net	(6,369)	449	1,972
Provision for inventories	733	2,610	1,023
Other non-cash items	290	76	81
Loss on extinguishment of term loan	0	1,367	0
Changes in operating assets and liabilities:
Accounts receivable	(5,094)	(2,506)	(19,137)
Inventories	1,647	(14,730)	(22,042)
Prepaid expenses and other assets	739	(1,215)	1,860
Accounts payable	5,312	(1,281)	(3,066)
Accrued payroll and related benefits	(2,515)	(3,428)	8,103
Accrued expenses and other current liabilities	(2,621)	1,811	5,889
Accrued warranty liability	91	(83)	791
Deferred revenue	3,015	2,161	2,881
Operating lease liabilities	(1,347)	(1,150)	(882)
Accrued interest	0	(721)	0
Net cash used in operating activities	(131,373)	(145,729)	(130,264)
Cash flows from investing activities:
Purchases of property and equipment	(3,440)	(8,325)	(3,108)
Purchases of investment securities	(172,284)	(261,154)	(178,432)
Maturities of investment securities	258,750	203,184	39,033
Net cash (used in) provided by investing activities	83,026	(66,295)	(142,507)
Cash flows from financing activities:
Proceeds from stock option exercises and ESPP purchases	10,427	8,042	11,062
Proceeds from issuance of term loan, net of issuance costs	33,225	96,059	0
Repayment of term loan and extinguishment costs	0	(31,203)	0
Proceeds from issuance of common stock upon the follow-on public offering, net of issuance costs	0	0	149,085
Net cash provided by financing activities	43,652	72,898	160,147
Net decrease in cash, cash equivalents and restricted cash	(4,695)	(139,126)	(112,624)
Cash, cash equivalents and restricted cash as of beginning of period	76,533	215,659	328,283
Cash, cash equivalents and restricted cash as of end of period	71,838	76,533	215,659
Supplemental cash flow disclosures:
Cash paid for income taxes	491	385	83
Cash paid for interest	10,847	3,185	1,146
Cash paid for amounts included in the measurement of operating lease liabilities	1,347	1,150	882
Supplemental non-cash investing and financing activities:
Capital expenditures included in accounts payable and accrued expenses	159	167	121
Right-of-use assets obtained in exchange for lease liabilities	528	0	0
Transfer of inventories to property and equipment	119	28	1,410
Deferred financing costs included in accrued expenses	0	750	0
Transfer of property and equipment to inventories	$ 0	$ 199	$ 1,192