Organization and Basis of Presentation - Narrative (Details) mi in Thousands, customer in Thousands		3 Months Ended		9 Months Ended
	Oct. 18, 2021 USD ($) agreement	Sep. 30, 2021 USD ($) company transmissionCenter MW	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) company customer transmissionCenter mi MW	Sep. 30, 2020 USD ($)
Property, Plant and Equipment [Line Items]
Length of transmission lines | mi				24
Number of regional transmission centers | transmissionCenter		2		2
Capitalized cost of equity		$ 13,000,000	$ 13,000,000	$ 34,000,000	$ 36,000,000
Capitalized interest		$ 7,000,000	$ 8,000,000	$ 20,000,000	$ 21,000,000
Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Number of agreements | agreement	6
Maximum amount borrowed under revolving credit facility	$ 4,500,000,000
Revolving Credit Facility | Line of Credit | First Energy and FET | Subsequent Event
Property, Plant and Equipment [Line Items]
Maximum amount borrowed under revolving credit facility	$ 1,000,000,000
PN | Waverly, New York
Property, Plant and Equipment [Line Items]
Number of customers served by utility operating companies | customer				4
Parent, the Utilities, FET and Certain Subsidiaries | Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Debt term	5 years
The Ohio Companies | Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Maximum amount borrowed under revolving credit facility	$ 800,000,000
The Pennsylvania Companies | Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Maximum amount borrowed under revolving credit facility	950,000,000
JCP&L | Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Maximum amount borrowed under revolving credit facility	500,000,000
MP and PE | Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Maximum amount borrowed under revolving credit facility	400,000,000
Transmission Companies | Revolving Credit Facility | Line of Credit | Subsequent Event
Property, Plant and Equipment [Line Items]
Maximum amount borrowed under revolving credit facility	$ 850,000,000
Regulated Distribution
Property, Plant and Equipment [Line Items]
Number of existing utility operating companies | company		10		10
Number of customers served by utility operating companies | customer				6,000
Plant capacity (in MW's) | MW		3,580		3,580