Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net loss		$ (131,755)	$ (55,356)	$ (55,489)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation		30,692	22,912	11,638
Depreciation of property and equipment		3,139	797	550
Non-cash lease expense		1,583	1,970	1,092
Non-cash interest (income) expense, net		4,349	1,490	(1,499)
Changes in assets and liabilities:
Accounts receivable, net		(274)	39	(176)
Accounts receivable from related party		(11)	(32)	2,058
Inventory		(851)	0	0
Prepaids and other current assets		1,672	(2,492)	719
Other assets		(86)	(49)	61
Accounts payable		2,610	2,982	188
Operating lease liabilities		10,646	10,270	(1,114)
Other liabilities		3,487	576	5,573
Deferred revenue from related party		(822)	(64,250)	(33,724)
Net cash used in operating activities		(75,621)	(81,143)	(70,123)
Investing activities
Purchases of property and equipment, net		(19,020)	(15,409)	(790)
Purchases of investments		(307,449)	(445,671)	(211,973)
Sales of investments		0	0	4,967
Maturities of investments		418,688	178,720	195,270
Net cash provided by (used in) investing activities		92,219	(282,360)	(12,526)
Financing activities
Proceeds from issuance of common stock		0	325,654	73,276
Proceeds from exercise of stock options and employee stock purchase plan		7,405	30,318	22,857
Employees' tax withheld and paid for restricted stock units		(5,273)	(3,709)	(1,313)
Borrowings under credit facility agreement, net of issuance costs		0	4,358	0
Payments of long-term debt		(1,049)	0	0
Net cash provided by financing activities		1,083	356,621	94,820
Net increase (decrease) in cash, cash equivalents and restricted cash		17,681	(6,882)	12,171
Cash, cash equivalents and restricted cash at beginning of period		33,377	40,259	28,088
Cash, cash equivalents and restricted cash at end of period		51,058	33,377	40,259
Supplemental disclosures of cash flow information
Cash paid for interest		2,027	1,947	1,735
Right-of-use assets obtained in exchange for lease obligations	[1]	522	27,177	2,796
Purchases of property and equipment, net recorded in accounts payable and accrued liabilities		$ 0	$ 8,394	$ 378

[1] Amounts for the year ended December 31, 2019 include the transition adjustment of $1,301 for the adoption of Accounting Standards Codification (ASC) Topic 842 Leases (ASC 842).