copyright

Okay, you probably will be thinking by the end of this posting that the guy is nothing more than a wannabe who has not been around the block, wants to get rich quick, etc. etc. but heres the situation. I have been teaching ESL for five years now here in Mexico. I have an idea for a learning program I have never seen in any bookstore. It is directed for the intermediate to advanced student. No, I am not going to tell you anymore than that. Should I do so, I would jeopardize a copyright to the concept. I have visited New Options Bookstore, Gandhi Books, Londres Bookstore in Merida, the American Bookstore, and dozens more that deal specifically with texts for the non native English speaker. Never have I seen my idea on the shelf. The question is, without having the means to copywright the idea which would involve the expenditure of 10s of thousands of dollars to create, how would I go about doing so without jeopardizing my future copywright.
If I pitch this idea to Oxford, Longman, Cambridge, etc. etc. what is there to protect me from their stealing the idea without financial renumeration?