Sharpe on a trading book

A bit of a dumb question, but for those of you who switched over from the sell side, how did you think about the Sharpe on your trading book at the bank when discussing your track records? Did you look at it in absolute dollar returns/stdevs or did you make assumptions about the book size?  For derivatives books that operate day to day on margin or credit lines it gets even murkier and that's before you get into the issues of distinguishing between actual risk taking and client activity. 

Thanks