Does this fit standard 8/12 x 11 document laying flat?

It shows you the internal and external measurements in the product info. But to answer your question, no. It looks as if the internal measurements are only 7" x 11". The papers will fit length wise if they are 11" or less but will not lay perfectly flat width wise if they are 8" wide. On any safe you look at, the internal and external dimensions will be listed under the "product info" tab. They do have bigger ones. Just have to find one is all.