Stockholders' equity (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding	33,077,886	25,795,553	33,077,886	25,795,553	7,977,990
Stock-based compensation expense	$ 199,207	$ 1,412,601	$ 1,053,508	$ 4,505,545
Unrecognized compensation expense	643,576		$ 643,576
Unrecognized compensation expense, recognition period			39 months 12 days
Personnel [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	199,207	1,296,473	$ 1,053,508	3,695,868
Discontinued Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0	$ 116,128	$ 0	$ 845,677