Variable interest entities (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Selling, General and Administrative Expenses [Member] | Biosciences [Member]
     
Variable Interest Entity [Line Items]      
Reclassified accumulated translation adjustments $ 83,000    
Oxford-Emergent Tuberculosis Consortium [Member]
     
Variable Interest Entity [Line Items]      
Assets of variable interest entities included in consolidated balance sheet 305,000 2,000,000  
Liabilities of variable interest entities included in consolidated balance sheet 249,000 2,000,000  
Net loss (1,800,000) (10,700,000) (13,200,000)
Net losses of variable interest entities included in consolidated statement of operations $ (910,000) $ (5,400,000) $ (6,700,000)