CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities:
Net loss	$ (740,867)	$ (581,784)	$ (357,937)
Non-cash adjustments reconciling net loss to operating cash flows
Non-cash consideration earned from license agreement	0	0	(11,424)
Change in fair value of long-term investment	4,753	7,411	(4,205)
Depreciation and amortization expense	2,929	1,781	641
Amortization of premium and accretion of discounts on investments	(4,200)	4,702	(674)
Share-based compensation expense	186,188	113,502	85,847
Loss on disposal of fixed assets	294	0	0
Foreign currency adjustments	(9,563)	0	0
Changes in operating assets and liabilities:
Accounts receivable, net	(865)	0	0
Inventory	(3,020)	0	0
Other current assets	(4,596)	(3,107)	(4,180)
Other long-term assets	(2,596)	(9,892)	(3,424)
Right-of-use asset	1,558	2,210	582
Lease liability	4,285	5,315	(652)
Accounts payable, accrued liabilities and other liabilities	(4,870)	71,062	23,895
Cash flows used in operating activities	(570,570)	(388,800)	(271,531)
Investing activities:
Purchases of short-term investments	(956,704)	(1,422,729)	(662,824)
Sales and maturities of short-term investments	1,187,358	843,623	527,334
Purchases of property and equipment	(4,851)	(9,795)	(4,367)
Cash flows provided by (used in) investing activities	225,803	(588,901)	(139,857)
Financing activities:
Proceeds from issuance of common stock, net of issuance costs	155,011	474,697	1,203,617
Proceeds from issuance of common stock under equity incentive plans	9,925	27,958	45,891
Proceeds from issuances under employee stock purchase plan	2,008	2,567	1,206
Cash flows provided by financing activities	166,944	505,222	1,250,714
(Decrease) increase in cash, cash equivalents and restricted cash	(177,823)	(472,479)	839,326
Cash, cash equivalents and restricted cash, beginning of year	413,703	886,182	46,856
Cash, cash equivalents and restricted cash, end of year	235,880	413,703	886,182
Reconciliation of cash, cash equivalents and restricted cash, end of year:
Cash and cash equivalents	235,260	413,083	885,562
Restricted cash included in other long-term assets	620	620	620
Total cash, cash equivalents and restricted cash	235,880	413,703	886,182
Supplemental disclosures of non-cash investing activities:
Accrued capital expenditures	0	583	292
Capitalized intangible asset included in accrued liabilities	15,000	0	0
Allowance utilized for tenant improvements	0	0	2,015
Initial recognition of operating right-of-use asset	0	0	39,890
Initial recognition of operating lease liability	$ 0	$ 0	$ 41,905