Significant agreements - Summary of Contract Assets and Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Contract liabilities:
Beginning Balance	$ 61,873,000	$ 71,340,000
Additions	95,960,000	12,099,000
Deductions	(26,976,000)	(14,463,000)
Impact of Exchange Rates	4,337,000	(7,103,000)
Ending Balance	135,194,000	61,873,000
Contract assets
Contract assets	0	0
Bayer collaboration deferred revenue
Contract liabilities:
Beginning Balance	0
Additions	45,000,000
Deductions	(1,160,000)
Impact of Exchange Rates	(222,000)
Ending Balance	43,618,000	0
Bayer collaboration deferred revenue | Deferred revenue material rights option
Contract liabilities:
Ending Balance	32,400,000
Novartis
Contract liabilities:
Beginning Balance	0
Additions	50,000,000
Deductions	(1,909,000)
Impact of Exchange Rates	1,917,000
Ending Balance	50,008,000	0
Novartis | Deferred revenue material rights option
Contract liabilities:
Ending Balance	33,200,000
Ionis collaboration deferred revenue
Contract liabilities:
Beginning Balance	21,489,000	34,115,000
Additions	960,000	99,000
Deductions	(10,734,000)	(9,347,000)
Impact of Exchange Rates	749,000	(3,378,000)
Ending Balance	12,464,000	21,489,000
Ionis collaboration deferred revenue | Deferred revenue material rights option
Contract liabilities:
Ending Balance	3,600,000
Genentech
Contract liabilities:
Beginning Balance	39,308,000	34,436,000
Additions		12,000,000
Deductions	(11,969,000)	(3,565,000)
Impact of Exchange Rates	1,765,000	(3,563,000)
Ending Balance	29,104,000	39,308,000
Genentech | Deferred revenue material rights option
Contract liabilities:
Ending Balance	21,800,000
Dementia Discovery Fund
Contract liabilities:
Beginning Balance	0	428,000
Deductions		(386,000)
Impact of Exchange Rates		(42,000)
Ending Balance	0	0
AstraZeneca
Contract liabilities:
Beginning Balance	1,076,000	2,361,000
Deductions	(1,204,000)	(1,165,000)
Impact of Exchange Rates	128,000	(120,000)
Ending Balance	$ 0	$ 1,076,000