Hmmm I really wouldn't call it an idiom. It's basically two turns of phrase in one. "As you please" basically means "as real/as much as you can imagine it". Given the context, the person isn't physically "big", but we do have an expression "larger than life" to mean that something/someone is "great" in some way. Because Jimmy Ringo is notorious, we can say he is "larger than life". His reputation makes him "larger" "...sitting in the local saloon, larger than life" makes perfect sense in this context, but misses the extra punch of "as you please".

It's not an idiom as such, simply quite an old-fashioned, informal expression to say that he was very big. It's not phrase that you here very much these days.