Variable interest entities (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Variable Interest Entity [Line Items]
Net loss	$ 13,491,000	$ 5,620,000	$ 15,042,000	$ 3,141,000
Oxford Emergent Tuberculosis Consortium [Member]
Variable Interest Entity [Line Items]
Ownership percentage of variable interest entity (in hundredths)			51.00%
Assets	308,000	1,600,000	308,000	1,600,000
Liabilities	243,000	2,800,000	243,000	2,800,000
Net loss		2,000,000	1,800,000	8,500,000
Net losses included in the Company's consolidated statement of operations		$ 1,000,000	$ 905,000	$ 4,300,000