Income taxes - Operating Loss Carryforwards (Details) - State and Local Jurisdiction $ in Thousands	Dec. 31, 2019 USD ($)
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 18,834
Tax Period One
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	2,664
Tax Period Two
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	6,577
Tax Period Three
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 9,593