XML 18 R1.htm IDEA: XBRL DOCUMENT v3.20.4
Cover Page - USD ($)
 12 Months Ended
Dec. 31, 2020
Jan. 31, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2020    
Document Transition Report false    
Entity File Number 333-21011    
Entity Registrant Name FIRSTENERGY CORP    
Entity Tax Identification Number 34-1843785    
Entity Incorporation, State or Country Code OH    
Entity Address, Address Line One 76 South Main Street    
Entity Address, City or Town Akron    
Entity Address, State or Province OH    
Entity Address, Postal Zip Code 44308    
City Area Code (800)    
Local Phone Number 736-3402    
Title of 12(b) Security Common Stock, $0.10 par value per share    
Trading Symbol FE    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 20,967,401,361
Entity Common Stock Shares Outstanding   543,215,090  
Documents Incorporated by Reference
Documents Incorporated By Reference
 PART OF FORM 10-K INTO WHICH
DOCUMENTDOCUMENT IS INCORPORATED
Proxy Statement for 2021 Annual Meeting of Shareholders of FirstEnergy Corp. to be held May 18, 2021Part III
    
Entity Central Index Key 0001031296    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Amendment Flag false