Cover Page	9 Months Ended
	Sep. 30, 2023 shares
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
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
Trading Symbol	FE
Security Exchange Name	NYSE
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
Entity Shell Company	false
Entity Common Stock Shares Outstanding	573,814,823
Entity Central Index Key	0001031296
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Amendment Flag	false