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Long-Term transition bonds are bonds under the Competition Act in which the proceeds of Transition Bonds are required to be used principally to reduce qualified stranded costs and the related capitalization of the utility. This represents the current and noncurrent portions. The initial maturity is beyond one year or beyond the normal operating cycle, if longer.

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Capitalization (Details Textuals)											3 Months Ended								12 Months Ended
Capitalization (Details Textuals)	Jan. 22, 2018 USD ($)	Jan. 16, 2018 $ / shares	Dec. 15, 2017 USD ($)	Oct. 05, 2017 USD ($)	Sep. 08, 2017 USD ($)	Jun. 21, 2017 USD ($)	Jun. 01, 2017 USD ($)	Mar. 15, 2017 USD ($)	Mar. 01, 2017 USD ($)	Dec. 13, 2016 USD ($) shares	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 USD ($) $ / shares shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2016 $ / shares	Dec. 31, 2017 USD ($) subsidiary $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 15, 2017 USD ($)	Aug. 31, 2017 USD ($)	May 16, 2017 USD ($)	Jun. 30, 2013 USD ($)
Debt Instrument [Line Items]
Retained earnings (accumulated deficit)											$ (6,262,000,000)				$ (4,532,000,000)				$ (6,262,000,000)	$ (4,532,000,000)
Dividends declared, in dollars per share \| $ / shares																			$ 1.44	$ 1.44	$ 1.44
Common stock dividends per share paid, in dollars per share \| $ / shares											$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.36
FERC-defined equity to total capitalization ratio																			35.00%
Preferred shares shares outstanding \| shares											0				0				0	0
Preference shares outstanding \| shares											0				0				0	0
Repayments of debt																			$ 2,291,000,000	$ 2,331,000,000	$ 879,000,000
Number of subsidiaries that issued environmental control bonds \| subsidiary																			2
Environmental control bonds outstanding											$ 383,000,000				$ 406,000,000				$ 383,000,000	406,000,000
Transition bond outstanding											56,000,000				85,000,000				56,000,000	85,000,000
Principal default amount specified in debt covenants																			100,000,000
Phase In Recovery Bonds
Debt Instrument [Line Items]
Long-term debt and other long-term obligations											$ 315,000,000				$ 339,000,000				$ 315,000,000	$ 339,000,000
Senior Notes
Debt Instrument [Line Items]
Face amount of loan						$ 3,000,000,000
Senior Notes \| 2.85% Senior Unsecured Notes Due 2022
Debt Instrument [Line Items]
Face amount of loan						$ 500,000,000
Interest rate (percent)						2.85%
Senior Notes \| 3.90% Senior Notes Due 2027
Debt Instrument [Line Items]
Face amount of loan						$ 1,500,000,000.0
Interest rate (percent)						3.90%
Senior Notes \| 4.85% Senior Notes Due 2047
Debt Instrument [Line Items]
Face amount of loan						$ 1,000,000,000
Interest rate (percent)						4.85%
Senior Notes \| 2.75% Senior Notes Due 2018
Debt Instrument [Line Items]
Repayments of Senior notes						$ 650,000,000
Interest rate (percent)						2.75%
AGC
Debt Instrument [Line Items]
FERC-defined equity to total capitalization ratio																			45.00%
FG \| PCRB
Debt Instrument [Line Items]
Repayments of Senior notes									$ 28,000,000
FG \| FMBs
Debt Instrument [Line Items]
Debt repaid							$ 130,000,000
MP \| FMBs
Debt Instrument [Line Items]
Debt repaid								$ 150,000,000
Face amount of loan																								$ 250,000,000
Interest rate (percent)																								3.55%
WP \| FMBs \| 275 Million FMBs, 4.14% Due 2047
Debt Instrument [Line Items]
Face amount of loan			$ 275,000,000
Interest rate (percent)			4.14%
WP \| FMBs \| 275 Million FMBs, 5.95% Due 2017
Debt Instrument [Line Items]
Interest rate (percent)			5.95%
Repayments of debt			$ 275,000,000
WP \| Senior Notes \| 100 Million FMBs, 4.09% Due 2047
Debt Instrument [Line Items]
Face amount of loan																						$ 0
Interest rate (percent)																						4.09%
JCP&L \| Senior Notes \| 5.65% Senior Notes Due 2017
Debt Instrument [Line Items]
Interest rate (percent)							5.65%
Repayments of debt							$ 250,000,000
ATSI \| Senior Notes \| 3.66% Senior Unsecured Notes Due 2032
Debt Instrument [Line Items]
Face amount of loan																							$ 150,000,000
Interest rate (percent)																							3.66%
PN \| Senior Notes \| 3.25% Senior Notes Due 2028
Debt Instrument [Line Items]
Face amount of loan					$ 300,000,000
Interest rate (percent)					3.25%
PN \| Senior Notes \| 6.05% Senior Notes Due 2017
Debt Instrument [Line Items]
Interest rate (percent)					6.05%
Repayments of debt					$ 300,000,000
CEI \| FMBs \| 300 Million FMBs, 7.88% Due November 2017
Debt Instrument [Line Items]
Debt repaid				$ 300,000,000
Interest rate (percent)				7.88%
CEI \| Senior Notes \| 3.50% Senior Notes Due 2028
Debt Instrument [Line Items]
Face amount of loan				$ 350,000,000
Interest rate (percent)				3.50%
Ohio Funding Companies \| Phase In Recovery Bonds
Debt Instrument [Line Items]
Face amount of loan																									$ 445,000,000
Common Stock
Debt Instrument [Line Items]
Stock issuance - employee benefits, shares \| shares																			2,989,893	2,685,946	2,457,827
Pension
Debt Instrument [Line Items]
Stock issuance - employee benefits, shares \| shares										16,097,875
Stock Investment Plan and certain share-based benefit plans										$ 500,000,000
Subsequent Event
Debt Instrument [Line Items]
Dividends declared, in dollars per share \| $ / shares		$ 0.36
Proceeds from issuance of equity	$ 2,500,000,000
Repayments of debt	$ 1,450,000,000