Significant agreements - Summary of Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Contract liabilities:
Beginning Balance	$ 71,340	$ 35,156	$ 35,156
Additions	0		49,056
Deductions	(3,860)		(11,697)
Deductions	(3,860)	(1,808)
Impact of Exchange Rates	(1,902)		(1,175)
Ending Balance	65,578		71,340
Ionis
Contract liabilities:
Beginning Balance	34,115
Additions	0
Deductions	(2,314)
Impact of Exchange Rates	(906)
Ending Balance	30,895		34,115
Genentech
Contract liabilities:
Beginning Balance	34,436	27,579	27,579
Additions	0		13,000
Deductions	(1,474)		(5,660)
Impact of Exchange Rates	(920)		(483)
Ending Balance	32,042		34,436
Dementia Discovery Fund
Contract liabilities:
Beginning Balance	428	821	821
Additions	0		0
Deductions	(72)		(391)
Impact of Exchange Rates	(10)		(2)
Ending Balance	346		428
AstraZeneca
Contract liabilities:
Beginning Balance	2,361	3,756	3,756
Additions	0		54
Deductions	0		(1,404)
Impact of Exchange Rates	(66)		(45)
Ending Balance	2,295		2,361
Ionis Evaluation and Option Agreement
Contract liabilities:
Beginning Balance	$ 34,115	$ 3,000	3,000
Additions			36,002
Deductions			(4,242)
Impact of Exchange Rates			(645)
Ending Balance			$ 34,115