Significant agreements - Summary of Contract Assets and Liabilities (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Contract liabilities:
Beginning Balance	$ 61,873,000	$ 71,340,000
Additions	50,000,000	12,099,000
Deductions	(4,896,000)	(14,463,000)
Impact of Exchange Rates	1,744,000	(7,103,000)
Ending Balance	108,721,000	61,873,000
Contract assets
Contract assets	0	0
Novartis Collaboration Agreement
Contract liabilities:
Beginning Balance	0
Additions	50,000,000
Deductions	0
Impact of Exchange Rates	467,000
Ending Balance	50,467,000	0
Ionis
Contract liabilities:
Beginning Balance	21,489,000	34,115,000
Additions	0	99,000
Deductions	(2,784,000)	(9,347,000)
Impact of Exchange Rates	425,000	(3,378,000)
Ending Balance	19,130,000	21,489,000
Genentech
Contract liabilities:
Beginning Balance	39,308,000	34,436,000
Additions	0	12,000,000
Deductions	(2,112,000)	(3,565,000)
Impact of Exchange Rates	829,000	(3,563,000)
Ending Balance	38,025,000	39,308,000
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	0	(1,165,000)
Impact of Exchange Rates	23,000	(120,000)
Ending Balance	$ 1,099,000	$ 1,076,000