v3.21.1
Summary of significant accounting policies - Marketable securities (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Summary of significant accounting policies    
Short-term marketable securities $ 0 $ 4,565
Unrealized gain, net of tax in accumulated other comprehensive loss   1
Income tax effect related to unrealized gains in accumulated other comprehensive loss   $ 0