Significant agreements - Summary of Contract Assets and Liabilities (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Contract liabilities:
Beginning Balance	$ 61,873,000	$ 71,340,000
Additions	95,870,000	12,099,000
Deductions	(16,293,000)	(14,463,000)
Impact of Exchange Rates	3,387,000	(7,103,000)
Ending Balance	144,837,000	61,873,000
Contract assets
Contract assets	0	0
Bayer Collaboration Agreement
Contract liabilities:
Beginning Balance	0
Additions	45,000,000
Deductions	0
Impact of Exchange Rates	(543,000)
Ending Balance	44,457,000	0
Bayer Collaboration Agreement | Deferred revenue material rights option
Contract liabilities:
Ending Balance	32,100,000
Novartis Collaboration Agreement
Contract liabilities:
Beginning Balance	0
Additions	50,000,000
Deductions	0
Impact of Exchange Rates	1,553,000
Ending Balance	51,553,000	0
Novartis Collaboration Agreement | Deferred revenue material rights option
Contract liabilities:
Ending Balance	33,000,000.0
Ionis
Contract liabilities:
Beginning Balance	21,489,000	34,115,000
Additions	870,000	99,000
Deductions	(5,341,000)	(9,347,000)
Impact of Exchange Rates	695,000	(3,378,000)
Ending Balance	17,713,000	21,489,000
Ionis | Deferred revenue material rights option
Contract liabilities:
Ending Balance	3,600,000
Genentech
Contract liabilities:
Beginning Balance	39,308,000	34,436,000
Additions	0	12,000,000
Deductions	(9,748,000)	(3,565,000)
Impact of Exchange Rates	1,554,000	(3,563,000)
Ending Balance	31,114,000	39,308,000
Genentech | Deferred revenue material rights option
Contract liabilities:
Ending Balance	22,000,000.0
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