I've attached a video showing the normal behavior when the Styles panel is attached, and then the buggy behavior when it's floating.
Basically, when you click in the Class to enter your new rule, the "tips" menu with Bootstrap classes appears. You click the rule you want, type your value and the menu vanishes. Normal behavior.
When the panel is detached, if you do the same thing, after you click your rule, when you type your value the "tips" menu remains visible. It won't automatically go away unless you re-dock the Style panel, or you can force close it by clicking somewhere neutral (so nothing is selected) and then click the "tips" menu again.
It was driving me crazy because I kept clicking it to close it not realizing at times my CSS rule was still in "editing mode" and I'd end up with with rules like
Video Link http://thelightwavegroup.com/images/tempvid2.mp4