Once idea you could do to see if the ideas are still in development stage, or if you're pushing at them, or even if they're pushing at you, is to sit down and do a very detailed outline of the book. What that'll do is force you to think out your story. If it has enough momentum to eventually translate into a book, you'll find that the story comes alive in your mind far beyond what it already is, and that the story will partially or completely hammer itself out right before your eyes.
The other option is, it might totally kill the idea, which really isn't a bad thing in the grand scheme of things. I've had several novels that were rattling around in my head and sounded like NYT best sellers only to die shortly after I started outlining them because I would begin fleshing out the idea only to realize how utterly retarded it was, or even that it wouldn't carry enough meat to be a viable store. Case in point. I had a story one time that was rattling around in my head called "Guardians Inc" and was about a group of mercenaries with mechas that went out and helped people. Well, when I started outlining the story, it very quickly became evident that I only had a scene or two worth of information and no story to back it up or go any further with. And no matter how much I pushed, nothing more of the idea would come out, so I simply canned the whole thing and moved on. That in turn then freed my mind up to work on other ideas, which subsequently spawned several other books that *did* go all the way from start to finish.
So go ahead and outline the book and get the thoughts in your mind down on paper, and don't be afraid thinking that doing so will kill your idea. Yes, it has that possibility, but at the same time it might turn that little twinkle into a skyscraper sized story.
