Segment information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Segment Reporting, Reportable Segments [Abstract]
Number of business segments | Segment	1
Long-lived assets	$ 2,229.4	$ 1,070.2
Revenue [Member] | Biothrax [Member]
Segment Reporting, Reportable Segments [Abstract]
Concentration risk percentage	45.00%	67.00%	80.00%
Revenue [Member] | United States [Member]
Segment Reporting, Reportable Segments [Abstract]
Concentration risk percentage	91.00%	89.00%	94.00%
Revenue [Member] | U.S. Government [Member]
Segment Reporting, Reportable Segments [Abstract]
Concentration risk percentage	76.00%	78.00%	86.00%
Product Sales [Member] | Biothrax [Member]
Segment Reporting, Reportable Segments [Abstract]
Concentration risk percentage	46.00%	68.00%	80.00%
Product Sales [Member] | ACAM2000 [Member]
Segment Reporting, Reportable Segments [Abstract]
Concentration risk percentage	19.00%	0.00%	0.00%
Product Sales [Member] | Other [Member]
Segment Reporting, Reportable Segments [Abstract]
Concentration risk percentage	35.00%	32.00%	20.00%
ForeignJurisdictions [Member]
Segment Reporting, Reportable Segments [Abstract]
Long-lived assets	$ 82.9	$ 28.6