Don't quit your job to pursue a startup unless:
1) You have a customer base lined up and some income is all but assured, or...
2) You have enough savings to get by for at least one year (including insurance) and a skill set or network that would enable you to jump back into a similarly desirable job right away.
Quitting with just an idea and strong cofounders is a recipe for disaster, stress, and misery. Remember, building is fun and easy, making sales isn't.
First whittle down what you really need to start (often times it's a lot less than you originally thought) and examine whether you really have to quit. If you are building something that your employer could lay claim to due to your employment agreement, it's a little more tricky, but if you are careful it is pretty easy to get around that.