How can I protect my website ideas?

I went to the website Guru.com and requested a quote from a web designer. I went into detail by showing him some of the concepts and (Microsoft Paint) Drawings of what I want the website to look like. I have the name and contact info of the web designer, as well as the e-mails and all the attachments I have sent him. I also own the domain name. What I am worried about is the fact that he could steal my concept and idea and turn it in as one of his own. What precautions should I take? How should I handle this to protect my idea from him taking it?