Fair value assumptions (Details)	9 Months Ended
Fair value assumptions (Details)	Sep. 30, 2014	Sep. 30, 2013
Fair value assumptions
Expected volatility minimum	113.93%	114.68%
Expected volatility Maximum	138.05%	194.14%
Expected dividends	0.00%	0.00%
Expected term minimum	3	3
Expected term maximum	5	5
Risk free rate minimum	0.41%	0.25%
Risk free rate maximum	0.59%	0.27%