When should I patent an idea? I foresee the possibility of an entertainment network attempting to cash-in on my idea without proper compensation.

You should speak with an intellectual property attorney to determine the best way (or ways) to protect your idea. As the other attorneys noted, generally ideas themselves are not generally protectible. However, their application may be protected by a patent, or their expression may be protected by copyright. Some inventions are protectible under several laws. For example, software code is protected by copyright and a computer system running the function embodied in the code may be eligible for a patent. You should work with a knowledgeable attorney to make sure that you obtain the broadest protection before you disclose your ideas to others.