Fair value of financial instruments (Details 4) - Recurring basis - Level 3 - Earnout liability - Monte Carlo - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Methodologies and significant inputs used in the determination of the fair value
Volatility (as a percent)	50.00%	50.00%	50.00%
Earnout Target 1	$ 13,700	$ 13,700	$ 13,700
Earnout Target 2	18,200	18,200	18,200
Fair value of liability at valuation date	$ 356	$ 314	$ 756
Minimum
Methodologies and significant inputs used in the determination of the fair value
Risk-free rate (as a percent)	0.09%	0.14%	0.15%
Time period from valuation until end of earnout	3 months	4 months 15 days	6 months
Discount rate	7.96%	8.18%	7.96%
Maximum
Methodologies and significant inputs used in the determination of the fair value
Risk-free rate (as a percent)	3.51%	3.00%	3.21%
Time period from valuation until end of earnout	9 years	9 years 4 months 15 days	9 years 6 months
Discount rate	11.39%	11.04%	11.03%