v3.19.2
Summary of significant accounting policies - Marketable securities (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Summary of significant accounting policies    
Short-term marketable securities $ 42,799 $ 0
Unrealized gains, net of tax in accumulated other comprehensive loss 45  
Income tax effect related to unrealized gains in accumulated other comprehensive loss $ 0