Additional paid-in capital (Details 1) - 6 months ended Jun. 30, 2015	Total
September 16, 2014 [Member]
Additional Paid In Capital [Line Items]
Expected volatility	120.60%
Risk-free rate	1.78%
Expected term (years)	5 years
Dividend yield	0.00%
August 13, 2013 [Member]
Additional Paid In Capital [Line Items]
Expected volatility	131.50%
Risk-free rate	1.49%
Expected term (years)	5 years
Dividend yield	0.00%