Other operating income - Narrative (Details) $ in Thousands	1 Months Ended						3 Months Ended		9 Months Ended		37 Months Ended
	Feb. 29, 2020 USD ($) option_segment	Jan. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Aug. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Sep. 30, 2017 USD ($) option_segment	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Income recognized in respect of BARDA							$ 1,607	$ 4,228	$ 7,715	$ 14,251
Grant
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Grant income							$ 143	$ 227	$ 334	$ 775
CARB-X
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Grant funding arrangement, maximum funding value					$ 4,500
Grant funding arrangement, committed funding base					$ 2,000
Grant funding arrangement, committed funding increase	$ 1,200
Grant funding arrangement, maximum funding value remaining	$ 2,500
Grant funding arrangement, number of option segments | option_segment	2
BARDA
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development arrangement, committed funding base						$ 32,000
Research and development arrangement, number of option segments | option_segment						3
Research and development arrangement, maximum funding value		$ 72,500	$ 63,700			$ 62,000
Research and development arrangement, committed funding increase		8,800	9,600	$ 12,000
Research and development arrangement, total committed funding		$ 62,400	$ 53,600
Research and development arrangement, funding received											$ 47,000
Income recognized in respect of BARDA											$ 42,800