CSS selector not working properly with not CSS selector

Question

I am trying to get the text within a certain div, however div contains another div inside and I do not want to get text in that nested div.

HTML:

<div id="description_tab" class="panel-collapse collapse in" style="" aria-expanded="true">
    <div class="panel-body">

        Text I want to select

       <div id="attributeSpec" class="visible-xs pt-3">

       Text I do not want to select  
                             
      </div>
   </div>
</div>

CSS selector:

#description_tab .panel-body:not(#attributeSpec)

This selector still gets all the text.