I replied not knowing how much you know or don't know... so I had some questions before trying to give an answer, they were not meant to be derogatory. John also made some suggestions which didn't seem to fully help you. So the reason I had some more questions is because there are more than a few ways to make things work the way you'd like... and it makes no sense to suggest a way that you're not using.
So, I definitely encourage you to continue reading the help and the manual... but if you can say when the lister is NOT showing in Details mode the way you want (give a specific example of when it works, or when it doesn't work) then we should be able to come up with the way that works for you. Between what John and I have both suggested... I thought something should have worked for you. We need more info on what's wrong...
Edit note- A lister 'layout' is a saved lister configuration which stores various elements of how a lister looks separately from a lot of the controls found in Opus preferences... things like the format controls (columns, sorting, view-mode). Changing these things in the Preferences or Folder Options might not work the way you'd expect if you are using a saved layout, and chances are if you don't know what a layout is... you probably were not using one 
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Edit note 2- And so if you're NOT using saved layouts, a good thing might be to take a look at Nudels 'Folder Format' FAQ at the following URL: