Alliant Energy Corporation operates as a regulated investor-owned public utility holding company. The Company's primary focus is to provide regulated electric and natural gas service to its customers in the Midwest through its two public utility subsidiaries: Interstate Power and Light Company (IPL) and Wisconsin Power and Light Company (WPL). Its segments include Utility, and ATC Holdings, Non-utility, Parent and Other. The Utility segment includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The Utility segment includes three operations: utility electric operations, utility gas operations and utility other. The ATC Holdings, Non-utility, Parent and Other segment includes the operations of Alliant Energy Finance, LLC (AEF) and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of the Company's interest in ATC Holdings.