Related party transactions (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Saudi Arabia [Member]
Dec. 31, 2013
Qatar [Member]
Dec. 31, 2013
United Arab Emirates [Member]
Dec. 31, 2011
Family Members of Executive Chairman [Member]
Dec. 31, 2011
Member of Board of Directors [Member]
Related Party Transaction [Line Items]          
Percentage of net sales of biodefense products subject to payment to related party (in hundredths) 17.50% 15.00% 15.00%    
Costs incurred from services rendered under marketing/consulting agreement       $ 35,000 $ 225,000