Commercial banks eased back slightly in their holdings of mortgage securities during the third quarter, although a number of large institutions padded their MBS portfolios and industry-wide holdings remained at historically high levels. According to data from the Federal Deposit Insurance Corp., commercial banks held $902.88 billion of mortgage securities as of the end of the third quarter. That was down 1.1 percent from the previous quarter, but significant buying activity in the first half… [Two data tables included]