Wisconsin Energy Corporation said on Monday that it would buy energy holding company Integrys Energy Group in a $9.1 billion deal, including debt, that is expected to expand the company’s geographic base.

The cash and stock deal calls for the Milwaukee-based Wisconsin Energy to pay 1.128 of its shares and $18.58 in cash for each share of Integrys—a 17.26 percent premium over the target’s closing price on Friday.