Chill, Relax, Nobody will steal your Idea, people are too busy to even care about your idea, it is all in your head and the earlier you bring the idea out and start working on it the better for you, you don't need to write to any non governmental organization or any one else, you should work on your idea yourself or maybe you should hire your friends to build it with you.
Understand that any partnership that you sign with the organizations above, they will have the upper hand and you'll be at disadvantage because you need them more than they need you.
So, you need to really think critically and ask questions like does my idea even makes any sense to start with.
An Idea is just an idea, everyone else has one what makes your own idea different that other people will even want to steal, execution is what really matters because it will project your idea to the world but how can you validate your idea with just an idea no any concept or prototype!?
And if you want to secure your idea you can patent it at the patent department I think their fee is between sixty to one hundred dollars