Summary of significant accounting policies (Details) $ in Thousands, Dose in Millions		3 Months Ended		9 Months Ended
	Mar. 16, 2017 USD ($) Dose	Sep. 30, 2017 USD ($) Segment	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Summary of significant accounting policies [Abstract]
Number of business segments | Segment		1
Product Information [Line Items]
Billed revenue amount		$ 114,296	$ 96,698	$ 259,875	$ 208,785
BioThrax [Member] | BARDA [Member]
Product Information [Line Items]
Amount of contract	$ 100,000
Period of performance	2 years
Consideration allocated to procurement	$ 93,600
NuThrax [Member] | BARDA [Member]
Product Information [Line Items]
Consideration allocated to development activities	$ 137,100		$ 147,500		147,500
NuThrax [Member] | BARDA [Member] | Minimum [Member]
Product Information [Line Items]
Number of doses to be delivered | Dose	2
NuThrax [Member] | BARDA [Member] | Maximum [Member]
Product Information [Line Items]
Number of doses to be delivered | Dose	3
Discount on purchase price for doses to be procured	$ 100,000
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax benefit associated with stock option activity					$ 3,500