Revenue (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue
Revenue accounted for under Topic 606		$ 333	$ 6,920	$ 525	$ 1,703	$ 797	$ 461	$ 847	$ 7,551	$ 9,481	$ 9,656	$ 5,319
Collaboration revenue
Revenue
Revenue accounted for under Topic 606										6,210	6,500
Collaboration revenue - Upfront payment
Revenue
Revenue accounted for under Topic 606										1,538
Collaboration revenue - Upfront payment | License Agreement | Sinovant Sciences, LTD
Revenue
Revenue accounted for under Topic 606	$ 5,000
Research premium
Revenue
Revenue accounted for under Topic 606										1,311	2,594	4,842
Government grants
Revenue
Revenue accounted for under Topic 606										$ 422	$ 562	369
Grants from WWFF
Revenue
Revenue accounted for under Topic 606												$ 108