USB (like WFC) has a business model that emphasizes non-interest income (WFC through cross-selling to their bank customers stuff like insurance and USB through its payments business which generates transaction income - eg trusts, debit cards, etc). So, in addition to strong deposit gathering and conservative credit underwriting, USB generates a significant amount of non-lending related income. In USB's case, they are growing this business rapidly and it creates a positive cycle as they can afford to be more choosy on their lending (which further reduces loan losses and gives them better lending returns as seen in the recent TARP results).
This business model tends to give USB a higher ROA and ROE in comparison to other banks and makes them a bit less reliant on pure lending. There's only a few non-investment-bank banks that do this. I would recommend you examine and compare a few of the big regional "pure" banks' income statements and try to see the difference (eg compare USB vs MTB, BBT, or PNC).
Hope this helps.
wabuffo