Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Taxes
Income tax expense (benefit)	$ 1,130	$ 1,460	$ (1,975)	$ 3,860
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	628.00%	30.50%	32.10%	29.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 400		$ 1,500