Significant agreements - Summary of Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Contract assets
Balance at the beginning of year	$ 0	$ 0
Additions	149	91
Deductions	(103)	(91)
Impact of exchange rates	0	0
Balance at the end of year	46	0
Change in Contract with Customer, Liability [Abstract]
Balance at the beginning of year	14,635	14,467
Additions	1,138	5,350
Deductions	(5,596)	(4,472)
Impact of exchange rates	(314)	(710)
Balance at the end of year	9,863	14,635
AstraZeneca
Change in Contract with Customer, Liability [Abstract]
Balance at the beginning of year	4,727	0
Additions	24	5,350
Deductions	(35)	(466)
Impact of exchange rates	(167)	(157)
Balance at the end of year	4,549	4,727
Sanofi
Change in Contract with Customer, Liability [Abstract]
Balance at the beginning of year	9,908	14,467
Additions	0	0
Deductions	(5,286)	(4,006)
Impact of exchange rates	(116)	(553)
Balance at the end of year	4,506	9,908
Dementia Discovery Fund
Change in Contract with Customer, Liability [Abstract]
Balance at the beginning of year	0
Additions	1,114
Deductions	(275)
Impact of exchange rates	(31)
Balance at the end of year	$ 808	$ 0