FirstEnergy Corp. is a holding company. The Company is engaged in holding, directly or indirectly, all of the outstanding equity of its principal subsidiaries. Its segments include Regulated Distribution, Regulated Transmission, Competitive Energy Services (CES) and Corporate/Other. As of December 31, 2016, the Regulated Distribution segment distributed electricity through the Company's 10 utility operating companies, serving approximately six million customers, and purchased power for its provider of last resort (POLR), standard offer service (SOS), standard offer service (SSO) and default service requirements in Ohio, Pennsylvania, New Jersey and Maryland. The Regulated Transmission segment transmits electricity through transmission facilities owned and operated by American Transmission Systems, Incorporated (ATSI) and Trans-Allegheny Interstate Line Company (TrAIL). The CES segment primarily supplies electricity to end use customers through retail and wholesale arrangements.