Nature of business - Recently adopted Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2019
Operating lease liability		$ 2,046
Right of use assets		$ 1,792
ASU 2016-02 | Restatement Adjustment
Operating lease liability	$ 2,100
Right of use assets	1,900
ASU 2018-02
Reclassification from AOCI to Retained earnings	$ 100