Commonwealth Bank confirmed yesterday that Rob De Luca, the bank's executive general manager, retail and business banking, will become managing director of the bank's subsidiary, Bankwest. CBA said De Luca would take over from Jon Sutton in March.Sutton will take on an unspecified role within CBA. The Australian Financial Review first reported on the selection of De Luca in October.Bankwest contributed A$463 million to group earnings of $6.8 billion last financial year - a turnaround from a loss of $45 million in 2009/10.Bankwest makes a disproportionately large contribution to CBA provisions. Out of a total of $2.1 billion in the June half last year, $979 million came from Bankwest. It accounted for one-third of impaired assets during the same period.CBA has done of lot of work to "de-risk" the Bankwest loan portfolio, culling more than 20 per cent of its business book.It will be swept up in the CBA core banking transformation in 2013.Bankwest is a significant driver of new business growth for CBA, however. It reported eight per cent growth in new lending in the year to June, while group volume was down 3.8 per cent.And its mortgage book has grown at more than twice the rate of system growth over the past year, while the group has lagged system.Its role in the group is to give the bank "exposure to fast-growing sectors of the economy".But one of its weaknesses is a relatively small number of products per customer. CBA has 2.64 products per customer, while Bankwest has 2.25, which is lower than that of all CBA's big bank peers.