Unfortunately there are a million ideas out there in this area. The idea isn't worth anything. It's the implementation. And no, nobody will want to steal it. Being secretive makes you sound like you don't know what you're doing.
Game studios won't even listen to your idea - mostly out of fear that if they ever did anything remotely like what someone once pitched they would be sued. So as SOP, game studios will not hear you out. It doesn't work like Hollywood, where you can write a screenplay and shop it around.