CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities:
Net loss	$ (364,831)	$ (302,110)
Non-cash adjustments reconciling net loss to operating cash flows
Change in fair value on long-term investment	5,583	6,682
Depreciation of property and equipment	1,322	705
Amortization of premium and accretion of discounts on investments	1,457	2,225
Share-based compensation expense	81,589	52,691
Loss on disposal of fixed assets	295	0
Changes in operating assets and liabilities:
Other current assets	(4,955)	(68,047)
Other long-term assets	(1,194)	(8,550)
Right-of-use asset	857	1,185
Lease liability	2,905	2,578
Accounts payable, accrued liabilities and other liabilities	(26,989)	108,858
Cash flows used in operating activities	(303,961)	(203,783)
Investing activities:
Purchases of short-term investments	(341,472)	(765,888)
Sales and maturities of short-term investments	496,834	352,258
Purchases of property and equipment	(2,801)	(5,137)
Cash flows provided by (used in) investing activities	152,561	(418,767)
Financing activities:
Proceeds from issuance of common stock under equity incentive plans	2,924	16,494
Proceeds from issuances under employee stock purchase plan	995	1,214
Cash flows provided by financing activities	3,919	17,708
Decrease in cash, cash equivalents and restricted cash	(147,481)	(604,842)
Cash, cash equivalents and restricted cash, beginning of period	413,703	886,182
Cash, cash equivalents and restricted cash, end of period	266,222	281,340
Reconciliation of cash, cash equivalents and restricted cash, end of period:
Cash and cash equivalents	265,602	280,720
Restricted cash included in other long-term assets	620	620
Total cash, cash equivalents and restricted cash	266,222	281,340
Supplemental disclosures of non-cash investing activities:
Accrued capital expenditures	$ 154	$ 0