Idea can't be a subject of a patent. To protect it with a patent, you need to have at least a prototype of a product which this idea is supposed to be at the end.
You should comprehend that idea itself worth nothing and isn't material. Because tommorow my brain can generate the exact idea that you have today. And no one can protect you from another's mind.
There is another side of this question. Everybody in the world got an idea. And before someone will want to steal stranger's idea, he need to be told why this particular stranger's idea is better than his own one. He need to know why he should work with your idea and not with his own one. And mostly one chooses to work with his own ideas, since he understands them more correctly just because he generated them himself.
And it's highly unlikely that a developer you want to hire will tell you that he don't want to work with you, then take your idea and make a product from it. Because if he's a really good developer, he got dozens of ideas himself.
Moreover, development process is very complicated thing that is consisted of many decisions that developers, managers and stakeholder constantly making. Everyone can take your idea, but no one is able to make the same decisions you make. Thus, no one can make the same product you want to make.