CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities:
Net loss	$ (188,386)	$ (135,680)
Non-cash adjustments reconciling net loss to operating cash flows
Change in fair value on long-term investment	5,077	3,953
Depreciation of property and equipment	629	294
Amortization of premium and accretion of discounts on investments	982	1,001
Share-based compensation expense	42,905	24,722
Changes in operating assets and liabilities:
Other current assets	0	(2,810)
Other long-term assets	(1,584)	(8,149)
Increase (Decrease) in Right-of-use Assets	451	612
Increase (Decrease) in Operating Lease Liability	1,431	1,270
Increase (Decrease) in Accounts Payable and Accrued Liabilities	(21,974)	4,371
Cash flows used in operating activities	(160,469)	(110,416)
Investing activities:
Purchases of short-term investments	(212,545)	(621,661)
Sales and maturities of short-term investments	263,240	167,240
Purchases of property and equipment	(1,140)	(1,107)
Cash flows provided by (used in) investing activities	49,555	(455,528)
Financing activities:
Proceeds from issuance of common stock under equity incentive plans	2,527	9,885
Cash flows provided by financing activities	2,527	9,885
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	(108,387)	(556,059)
Cash, cash equivalents and restricted cash, beginning of period	413,703	886,182
Cash, cash equivalents and restricted cash, end of period	305,316	330,123
Reconciliation of cash, cash equivalents and restricted cash, end of period:
Cash and cash equivalents	304,696	329,503
Restricted cash included in other long-term assets	620	620
Total cash, cash equivalents and restricted cash	305,316	330,123
Supplemental disclosures of non-cash investing activities:
Accrued capital expenditures	$ 842	$ 439