Stock-based compensation (Details 3) - $ / shares	3 Months Ended	9 Months Ended
	Jun. 30, 2015	Sep. 30, 2015
Number of Shares
Exercised/Converted	(895,655)
Employee Stock Options.
Number of Shares
Beginning Balance		4,899,713
Granted		256,780
Exercised/Converted		(102,711)
Cancelled/Forfeited		(126,677)
Ending Balance		4,927,105
Weighted Average Exercise Price
Beginning Balance		$ 4.07
Granted		5.27
Exercised/Converted		4.32
Cancelled/Forfeited		4.67
Ending Balance		$ 4.11
Restricted stock units [Member]
Number of Units
Beginning Balance		655,729
Granted		204,434
Exercised/Converted		(547,828)
Cancelled/Forfeited		(23,602)
Ending Balance		288,733
Weighted Average Exercise Price
Beginning Balance		$ 6.19
Granted		6.66
Exercised/Converted		6.05
Cancelled/Forfeited		5.37
Ending Balance		$ 6.85