Having been a banking exec for the past 20 odd years, I would suggest two things:
1) First get hold of a satisfactory confidentiality and non-disclosure agreement (to be reviewed by a competent lawyer) which everyone you speak to will have to sign before they hear a word of your idea; and
2) Seek your initial financing from family, friends and associates. Venture capital firms, even the smaller boutiques, are deluged with requests from budding entrepreneurs and frankly, most of them strongly prefer only those applicants who have some history under their belt of prior successful start-ups. They will, on occasion, take on a new project if an idea is just truly outstanding for its time, however you and/or your partners in this venture will need some background in business planning and management for them to even consider entrusting any amount of capital to your new venture.
The items mentioned by others here about a business plan with a budget, etc.. are all on target once you are serious and don't forget, those things are just as necessary for you and your venture as they are to the VC firm.
Good luck to you and if you really believe it is a good idea, then don't dally any further and get a move on before someone else thinks up the same idea and gets rich with it!
Happy Trading
