Edison Mission Energy, a power company that operates in Illinois and several other U.S. states, has filed for Chapter 11 banktruptcy protection as it tries to restructure about $5 billion in debt.

Edison Mission, the Santa-Ana Calif.-based unregulated power generation business of Edison International, owns and operates coal, natural gas and renewable power plants totaling more than 10,000 megawatts in states including California, Illinois, Pennsylvania and West Virginia. It is the parent of Midwest Generation, which manages several coal-fired plants in Illinois.

In its bankruptcy petition, the company listed assets of $5.1 billion and liabilities of $5 billion.