Stock-based compensation (Details 1) - Employee Stock Option [Member]	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at the beginning of period -Options | shares	17,600
Granted - Options | shares	12,831
Exercised - Options | shares	(2,129)
Forfeited/expired - Options | shares	(16,217)
Outstanding at the ending of period -Options | shares	12,085
Exercisable-Options | shares	0
Outstanding-Weighted Average Exercise Price at the beginning of period - Options | $ / shares	$ 12.02
Granted-Weighted Average Exercise Price | $ / shares	9.42
Exercised-Weighted Average Exercise Price | $ / shares	8.35
Forfeited/expired-Weighted Average Exercise Price | $ / shares	10.18
Outstanding-Weighted Average Exercise Price at the ending of period - Options | $ / shares	12.38
Exercisable-Weighted Average Exercise Price | $ / shares	$ 0
Outstanding-Weighted Average Remaining Contractual Life (Years)	2 years 2 months 19 days
Exercisable-Weighted Average Remaining Contractual Life (Years)	0 years
Outstanding-Aggregate Intrinsic Value | $	$ 3,658	[1]
Exercisable-Aggregate Intrinsic Value | $	$ 0	[1]

[1] The intrinsic value of a stock option represents the amount by which the fair value of the underlying stock, measured by reference to the closing price of the common shares of $12.60 on the Nasdaq Global Select Market on December 31, 2017, exceeds the exercise price of the option.