As I far as I know detaching is achieved in one of two ways. Hit the lowest icon in the image I have attached. It should be on the left hand side of the ID pane in Mac. It will disappear from the icons once detached.
Screen Shot 2014-05-14 at 8.30.56 AM.jpg 10.08KB
The other way is to click and hold over an item in the text. This is controlled by a preference. If you have an attached ID when you do this it will go away in favour of the popover version.
Reattaching does not appear to be by dragging for redocking as far as I could tell. But if you close the ID popover and then reopen ID - tool bar, key shortcut etc. then it will reattach.
Some in you original post caught my eye though :
"I found that the Instant Details pane was attached to the text window(s) above, attached at the bottom."
I've only ever seen ID on the bottom or to the right, never at the top. That I don't know how to do. Did I misread this sentence and you meant something else ?
Also check out file:///Applications/Accordance.app/Contents/Resources/Accordance%20Help/Default.htm#topics/04_gswa/using_insdet_palette.htm?Highlight=instant%20details but it does not explicitly describe reattach procedure.
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Accordance Configurations :
Mac : 2009 27" iMac Windows : HP 4540s laptop
Intel Core Duo Intel i5 Ivy Bridge
12GB RAM 8GB RAM
Accordance 11.1.5 Accordance 11.1.5
OSX 10.10.5 (Yosemite) Win 7 Professional x64 SP1