Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (205,808)	$ (202,611)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of contingent consideration	369	(3,108)
Depreciation and amortization	5,360	4,880
Stock-based compensation expense	42,527	36,293
(Gain) loss on equity securities	(28,372)	4,520
Other non-cash items	2,513	(1,387)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(8,979)	(9,285)
Inventory	(7,103)	(1,699)
Operating lease right-of-use assets	8,098	5,842
Accounts payable	67	(9,519)
Accrued expenses and other liabilities	(184)	(20,557)
Operating lease liabilities	(9,306)	(5,070)
Deferred revenue	(990)	(2,118)
Collaboration research advancement	(1,519)	(2,302)
Net cash used in operating activities	(203,327)	(206,121)
Cash flows from investing activities:
Purchase of property, plant and equipment	(7,626)	(10,676)
Purchases of marketable securities	(53,200)	(101,421)
Proceeds from maturities of marketable securities	350,860	336,675
Proceeds from sales of marketable securities	31,318	0
Net cash provided by investing activities	321,352	224,578
Cash flows from financing activities:
Proceeds from exercise of stock options and ESPP contributions	3,796	963
Net cash provided by financing activities	3,796	963
Increase in cash, cash equivalents and restricted cash	121,821	19,420
Cash, cash equivalents and restricted cash at beginning of period	373,728	381,709
Cash, cash equivalents and restricted cash at end of period	495,549	401,129
Reconciliation of cash, cash equivalents and restricted cash:
Total cash, cash equivalents and restricted cash	495,549	401,129
Supplemental cash flow disclosures from investing and financing activities:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	2,238	1,125
Right-of-use assets obtained in exchange for operating lease liabilities	22,049	14,425
Issuance of unrestricted stock awards to settle accrued employee compensation	$ 12,013	$ 0