Required documents and where to keep them?

Maybe this is a question for those of us in the States, but I have seen conflicting information on what documents to always have while riding (i.e. registration, proof of insurance) and then also where to keep them. Do y'all keep them in a pocket while you ride in case you get stopped and need them, or do you keep them on the bike? The only place that I could find on the bike was in a ziplock bag under the pillion seat but even that was so small it was pushing it to get them to fit.

Thanks!