Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
OPERATING ACTIVITIES:
Net loss			$ (245,197)	$ (172,135)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	$ 2,800	$ 1,600	7,735	4,166
Stock-based compensation expense			15,049	3,037
Change in the estimated fair value of contingent consideration			10,080	16,672
Change in the estimated fair value of success payment liabilities			57,698	40,637
Non-cash expense for operating lease right-of-use assets			4,597	2,889
Other non-cash items, net			(2,255)	819
Changes in operating assets and liabilities:
Prepaid expenses and other assets			(2,985)	682
Operating lease right-of-use assets and liabilities			5,028	91
Accounts payable			1,397	2,414
Accrued expenses and other liabilities			7,898	305
Net cash used in operating activities			(140,955)	(100,423)
INVESTING ACTIVITIES:
Purchases of marketable securities			(414,437)	(307,398)
Proceeds from sales and maturities of marketable securities			266,960	56,400
Purchases of property and equipment			(24,660)	(14,606)
Net cash used in investing activities			(172,137)	(265,604)
FINANCING ACTIVITIES:
Proceeds from initial public offering of common stock, net of offering costs			626,405
Proceeds from issuance of convertible preferred stock, net of issuance costs				435,538
Proceeds from exercise of stock options			2,227	46
Net cash provided by financing activities			628,632	435,584
Net increase in cash, cash equivalents, and restricted cash			315,540	69,557
Cash, cash equivalents, and restricted cash at beginning of period			126,949	81,807	$ 81,807
Cash, cash equivalents, and restricted cash at end of period	$ 442,489	$ 151,364	442,489	151,364	$ 126,949
SUPPLEMENTAL CASH FLOW DISCLOSURES:
Right-of-use assets obtained in exchange for operating lease liabilities			26,257	23,049
Cash received from lessor for tenant improvement allowance			5,160	91
Tenant improvement allowance included in operating lease liabilities			4,438	8,515
Purchases of property and equipment included in accounts payable and accrued liabilities			$ 3,231	$ 4,238