I'm wondering where these detailed informations come from. I don't remember that there were that much financial details in Tacitus, Suetonius and al. (though I didn't reread them recently).
This is the same feeling I often get watching history channel or the likes. Sometime I wish I was an historian, because some level of details and certain conclusions on facts happened thousands of years ago just sounds made up for entertainment purposes. I'm wrong, obviously, but I'd like to see somebody with the right knowledge trying to prove the contrary.
How sad to become old :) It's there in Tacitus' Annals, book 6, chapters XVI and XVII; Suetonius, life of Tiberius, chapter XLVIII. No mention of the bankers' names though.