Stockholders' equity (Details) - shares	Sep. 30, 2015	Dec. 31, 2014
Stockholders Equity Details
Options to purchase common stock	24,614
Options reserved for future issuance under the Company's 2007 Incentive Plan	77,687
Warrants to purchase common stock	8,380,000	26,769,000
Total reserved for future issuance	110,681