v3.19.1
Summary of significant accounting policies - Foreign currency translation (Details) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Foreign currency translation    
Cumulative foreign currency translation adjustments, net of tax in accumulated other comprehensive loss $ (1,333) $ (1,295)
Income tax effect related to foreign currency translation adjustments $ 0 $ 0