Significant agreements - Summary of Contract Assets and Liabilities (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Contract liabilities:
Beginning Balance	$ 61,873,000	$ 71,340,000
Additions	95,870,000	12,099,000
Deductions	(21,645,000)	(14,463,000)
Impact of Exchange Rates	(1,326,000)	(7,103,000)
Ending Balance	134,772,000	61,873,000
Contract assets
Contract assets	0	0
Bayer Collaboration Agreement
Contract liabilities:
Beginning Balance	0
Additions	45,000,000
Deductions	(434,000)
Impact of Exchange Rates	(2,045,000)
Ending Balance	42,521,000	0
Bayer Collaboration Agreement | Deferred revenue material rights option
Contract liabilities:
Ending Balance	31,000,000.0
Novartis
Contract liabilities:
Beginning Balance	0
Additions	50,000,000
Deductions	(772,000)
Impact of Exchange Rates	(178,000)
Ending Balance	49,050,000	0
Novartis | Deferred revenue material rights option
Contract liabilities:
Ending Balance	31,900,000
Ionis
Contract liabilities:
Beginning Balance	21,489,000	34,115,000
Additions	870,000	99,000
Deductions	(8,123,000)	(9,347,000)
Impact of Exchange Rates	227,000	(3,378,000)
Ending Balance	14,463,000	21,489,000
Ionis | Deferred revenue material rights option
Contract liabilities:
Ending Balance	3,500,000
Genentech
Contract liabilities:
Beginning Balance	39,308,000	34,436,000
Additions	0	12,000,000
Deductions	(11,112,000)	(3,565,000)
Impact of Exchange Rates	542,000	(3,563,000)
Ending Balance	28,738,000	39,308,000
Genentech | Deferred revenue material rights option
Contract liabilities:
Ending Balance	20,900,000
Dementia Discovery Fund
Contract liabilities:
Beginning Balance		428,000
Additions		0
Deductions		(386,000)
Impact of Exchange Rates		(42,000)
AstraZeneca
Contract liabilities:
Beginning Balance	1,076,000	2,361,000
Additions	0	0
Deductions	(1,204,000)	(1,165,000)
Impact of Exchange Rates	128,000	(120,000)
Ending Balance	$ 0	$ 1,076,000