I think you have the same problem I do. You see the big picture but its too broad and you don't see any details. You want to see the final product right away. At this point anything you write down comes nowhere near what you want.
"Take care of the little things and big things take care of themselves."
The best way I know how to explain it is with a rather awful metaphor of brick wall.
Bare with me please.
Your idea is this brick wall. You can imagine where it will sit and about long and high it will be. Problem is....you have no bricks to build your wall with. You start trying to put things down on paper but your idea is still to broad. If someone asked you the specifics you couldn't provide them.
I suggest starting with a frame or a skeleton, which I am pretty sure you already have one. Break your wall of an idea into sections. At first only divide it into a few parts. The big things: genre, theme. Then you break each of those sections down even further. Locations, time period/era. Then go even further. For each location: Factions/groups/species. For each of those do it again: sub-factions, ideologies, religions. For each of those: Key People/positions/ranks.
Keep breaking it down over and over again until you can't go further. When you get to that point, congrats. You just made a brick for your wall. Thing is about these bricks is that when you are done you won't end up with a pile of them. As you make them, they are already on the wall where they belong. Your wall/idea will be ready in no time. Woohoo! Awful Metaphor: Over!
As for names don't worry about thinking up a name for people or places. If you don't already have one in mind or can't come up with one on the spot for each of them, just give it a place holder you can go back and change it later. Describe it in detail. where is it? What does it do? What/who will be in/around it? What important events will happen in it or around it? Ask yourself these questions and any other you can think of and it might be easier to name it. And sometimes, it just might name itself.
Also let yourself be flexible, don't commit to anything(unless you absolutely have to =D). You might change your mind later. Will you add or take from it, trow it out completely or add something new?
Hope this helps...and that this was the problem XD
My problem is I can't follow through with any of this =/
um....I type way more then I intend to.