Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income taxes [Abstract]
Income tax provision	$ 115	$ 178
Effective tax rate	13.40%	20.70%
Unrecognized tax benefits that would favorably affect effective income tax rate if recognized	$ 105
Unrecognized tax benefits that will lapse upon expiration of statute of limitations	25
Accrued interest and penalties related to uncertain tax positions	$ 20