St George Bank began life as a building society selling home loans and it still likes to play on that heritage in its marketing. But at current growth rates the bank's institutional and business banking division will be the biggest profit producer for the bank within the next couple of years.In the latest half IBB produced pre-tax earnings of $294 million - 25 per cent ahead of the previous corresponding period. The retail banking division, whose pre-tax earnings were $379 million, could manage only six per cent growth.IBB's loan book grew 32 per cent, compared to 11 per cent for the retail mortgage book and 14.9 per cent for lending overall. IBB customer numbers have grown by an average of 23 per cent a year over the past four years and the number of products per customer has increased from 3.5 to 5 over the same period.With 16,000 customers, the average deal size in the division is $6 million.The bank's view is that strong customer satisfaction levels are the secret to the success of the business. It points to East & Partners research that shows no St George business customers indicating that they are likely to change banks, compared to an average of 17 per cent for the four majors.With average loan size of $6 million and 90 per cent of balances secured the bank is confident the IBB portfolio is conservatively positioned in the current market.But the business is getting bigger and runs the risk of suffering some growing pains if the economy goes into a prolonged slowdown. In 2004 only five per cent of IBB loans were over $50 million. Today 13 per cent of loans are bigger than $50 million. Forty-one per cent of loans are more than $20 million.Another factor the bank believes has led to success in this market is its use of industry specialist teams. It continues to add new teams, aiming more at the institutional end of the market.In the past couple of years it has put together an institutional property team and an acquisition finance team. It has a working capital services team that offers equipment finance, cashflow services, trade finance and transaction services.