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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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Regulatory Matters - Reliability and FERC Matters (Details) $ in Millions							3 Months Ended		12 Months Ended
	May 21, 2018	May 20, 2018	May 14, 2018	Feb. 20, 2018 USD ($)	Jun. 15, 2016 kv	Aug. 04, 2014	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) entity	Dec. 31, 2016	Dec. 31, 2015
Regulatory Matters [Line Items]
Regional enforcement entities \| entity									8
FERC
Regulatory Matters [Line Items]
Power threshold for cost methodology (in KW) \| kv					500
Denied recovery charges of exit fees									$ 78.8
FERC \| PJM Transmission Rates
Regulatory Matters [Line Items]
Load-ratio share										100.00%	50.00%
Solution-based distribution factor											50.00%
Gain related to litigation settlement							$ 42.0	$ 73.0	$ 115.0
Ohio Companies \| FERC \| Unit Power Agreement
Regulatory Matters [Line Items]
Term of proposed purchase power agreement						8 years
MAIT \| FERC
Regulatory Matters [Line Items]
Approved ROE	10.30%	11.00%
Approved capital structure	60.00%
JCP&L
Regulatory Matters [Line Items]
Approved ROE									9.60%
Approved capital structure									45.00%
JCP&L \| FERC \| Network Integration Transmission Service
Regulatory Matters [Line Items]
Annual revenue requirement				$ 135.0
JCP&L \| FERC \| PJM Tariff
Regulatory Matters [Line Items]
Annual revenue requirement				$ 20.0
Monogahela Power Company, Potomac Edison Company and West Penn Power Company \| FERC
Regulatory Matters [Line Items]
Requested rate increase (decrease) (percent)			6.70%