Condensed Consolidated Statements of Cash flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income (loss)	$ 17,144	$ (36,288)	$ 43,666	$ (50,570)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization expense			6,471	5,617
Stock-based compensation expense			9,320	9,186
Change in fair value of contingent consideration	4,242	15,347	(39,737)	5,895
Changes in operating assets and liabilities:
Collaboration receivables			2,568	(10,535)
Prepaid expenses and other assets			(8,521)	1,472
Right-of-use assets			6,210	270
Long-term prepaid rent			(2,395)	(7,381)
Accounts payable			3,900	(2,783)
Accrued expenses			1,571	4,013
Deferred revenue			(3,153)	(6,429)
Lease liability			(6,206)	(244)
Net cash provided by (used in) operating activities			13,694	(51,489)
Cash flows from investing activities:
Purchases of investments			(185,690)	(27,409)
Sales and maturities of investments			80,000	111,277
Purchases of property and equipment			(3,419)	(4,446)
Net cash provided by (used in) investing activities			(109,109)	79,422
Cash flows from financing activities:
Proceeds from public offerings, net of underwriting discounts and commissions				154,292
Payments of public offering costs				(443)
Proceeds from option exercises			2,369	5,831
Proceeds from issuance of common stock under employee stock purchase plan			490
Net cash provided by financing activities			2,859	159,680
Net increase (decrease) in cash, cash equivalents and restricted cash:			(92,556)	187,613
Cash, cash equivalents and restricted cash at beginning of period			346,853	85,530
Cash, cash equivalents and restricted cash at end of period	254,297	273,143	254,297	273,143
Cash, cash equivalents and restricted cash at end of period:
Cash and cash equivalents	249,471	272,193	249,471	272,193
Restricted cash	4,826	950	4,826	950
Total cash, cash equivalents and restricted cash at end of period	$ 254,297	$ 273,143	254,297	273,143
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses			$ 1,707	718
Offering costs included in accrued expenses				$ 238