O seguinte funciona para mim:
[Desktop Entry]
Version=15.0.2
Type=Application
Terminal=false
Icon[en_US]=/opt/idea-IU-143.1184.17/bin/idea.png
Name[en_US]=IntelliJ
Exec=/opt/idea-IU-143.1184.17/bin/idea.sh
Name=IntelliJ
Icon=/opt/idea-IU-143.1184.17/bin/idea.png
com as permissões mod:
sudo chmod 644 /usr/share/applications/intellij.desktop
sudo chown root:root /usr/share/applications/intellij.desktop
Referenciado de aqui