For the record, that is all fine and good to set expectations, but it won't actually give you any legal recourse unless you have an NDA (which most folks understandably will not sign) or something else showing that they AGREED they would not share the information. There are plenty of valid reasons that investors typically won't sign such a thing, and there is good information here http://venturehacks.com/articles/plans-ndas-traction.
Rules of thumb are (1) that ideas are just ideas and very few (no offense to anyone here) create a need to be concerned about having them stolen by an investor, and (2) for truly confidential information that could create problems for the company if the info got out (detailed financials, etc.). DON'T put that information in a pitch deck. Save that for later meetings where you actually might be able to get an NDA.