Capital structure (Details 3) (Common stock, USD $)	Dec. 31, 2014	Dec. 31, 2013
2014.
Warrants
Warrant shares		1,428
Exercise price (in dollars per share)		$ 128.00
2017
Warrants
Warrant shares	6,250	6,250
Exercise price (in dollars per share)	$ 128.00	$ 128.00
2019 and 2020
Warrants
Warrant shares	7,030	7,030
Exercise price (in dollars per share)	$ 128.00	$ 128.00
2019
Warrants
Warrant shares	130
Exercise price (in dollars per share)	$ 2,520.00
2014
Warrants
Warrant shares		452
Exercise price (in dollars per share)		$ 2,520.00