According to the following link I can enable this option: https://confluence.jetbrains.com/display/IntelliJIDEA/Working+with+Scala+Show+Type+Info+Action
But I have just installed IntelliJ 14.1 and there is no "IDE Settings" when I open the "Settings" dialog. Can someone tell me how to set this option in this version?
Yes, Scala settings have changed and most documentation is outdated.
I think the setting you are looking for is located here:
File ⇒ Settings ⇒ Languages & Frameworks ⇒ Scala ⇒ Editor Tab ⇒ Show type info on mouse hover after, ms