Billion dollar ideas are worth about a dime a billion. Everyone has them. Many, many of them are even great. Seldom do any of them become reality. People don't make money because they have an idea, they make money because they are capably of turning the idea into reality. The guy that mentioned Shark Tank gave a great example. Watch that show sometime, when someone has a great idea but no chance in hell of implementing it, the investors aren't interested.
If you really want to do something with the idea, you would be better looking for an inventors forum somewhere. That's where you'll find the type of experience your hoping to find.
The BHW forum is about making money by marketing online.
You won't like this idea, but it is more in line with the topic of this forum.
Create a website detailing and discussing your billion dollar idea. Use some whitehat or blackhat methods to promote the site and get traffic coming to it. Make a landing page that gets people interested, then make them do a CPA offer or something before they can access the rest of your site which includes even more details.
If the idea is good enough and starts creating a buzz, then monetize the site even more. Find some good clickbank products that are in a similar niche and advertize for them on your site. Ad some Adsense or other PPC advertising on the site to catch even more people just surfing through your site.
A Billion Dollar idea for a product you have no idea how to create isn't going to make you a billion dollars. If you think it is a good enough idea, then create a tos that has to be accepted before they access where you disclose the 'meat' of your idea. Include copyright info on your website explicitely protecting your content. That way if someone does actually implement the idea then you can document it was your idea.
In the meantime, by using the idea to market something else that does exists, you could very well make millions.