Concentration of credit risk (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Contract Revenues | Customer Concentration Risk | Collaboration Partner A
Concentration of risk
Percentage of concentration risk		28.00%
Contract Revenues | Customer Concentration Risk | Collaboration Partner B
Concentration of risk
Percentage of concentration risk		72.00%
Net Product Revenues | Customer Concentration Risk | Customer A
Concentration of risk
Percentage of concentration risk	22.00%	27.00%
Net Product Revenues | Customer Concentration Risk | Customer B
Concentration of risk
Percentage of concentration risk	13.00%	16.00%
Net Product Revenues | Customer Concentration Risk | Customer C
Concentration of risk
Percentage of concentration risk	14.00%	13.00%
Net Product Revenues | Customer Concentration Risk | Customer D
Concentration of risk
Percentage of concentration risk	11.00%	8.00%
Accounts Receivable | Credit Concentration Risk | Collaboration Partner A and B
Concentration of risk
Percentage of concentration risk	22.00%		47.00%
Accounts Receivable | Credit Concentration Risk | Customer A, B, C and D
Concentration of risk
Percentage of concentration risk	39.00%		25.00%