One of Iowa’s biggest businesses has sold off a big part of its operation. Principal Financial Group is selling its mortgage banking business to Citigroup for one-point-25 billion dollars. Principal executives say the sale will allow the company to focus on growth in its core businesses. About 15-hundred people are employed in Principal’s mortgage banking division — about one-thousand of those folks work in Des Moines. The execs say those employees will transfer over to Citigroup. The sale is expected to close in a few months, after federal regulators approve it. Citigroup says Principal Mortgage has about seven billion dollars worth of assets, much of that in the form of loans to homeowners. Principal is one of Iowa’s largest private employers with over 10-thousand workers on the payroll.