What Is Your Game Design Technique?
I will start by saying there is no correct technique. That will change with every team and every project. I can only offer a suggestion.
I think you've got these first two steps backwards. You will come up with a great idea, spend all this time on documentation, and then finally create a prototype, only to find out that while it sounds good on paper, it isn't fun. Now you've done a lot of work which you won't want to throw away, and you may end up trying really hard to make the game fun but fall short.
If it was me, I would pair up a designer and an artist, and have them create some prototypes. If you're not a programmer, just do it on paper. Exchange the games, play them, and see what you guys like. Once you've got a fun core idea, then you do all the documentation stuff.
I am speaking from experience here, having made many games that just aren't as fun as they were in my head.