Regulatory Matters (Details) - USD ($)			9 Months Ended
	Mar. 01, 2019	Jan. 22, 2019	Sep. 30, 2019	Dec. 31, 2018
Requested Distribution Modernization Rider annual revenue through filing		$ 199,000,000.0
Regulatory Assets, Noncurrent			$ 154,700,000	$ 152,600,000
Unbilled Revenue			15,200,000	16,800,000
Due from PJM transmission settlement			2,400,000	16,500,000
Refund of eligible excess ADIT and any related regulatory liability as required by the PUCO			65,100,000
Refund of eligible excess ADIT and any related regulatory liability as required by the PUCO, including taxes			83,200,000
Reduction of Long-term regulatory liability related to deferred income taxes			23.4
Subsidiaries [Member]
Requested Distribution Modernization Rider annual revenue through filing		$ 199,000,000.0
Regulatory Assets, Noncurrent			154,700,000	152,600,000
Unbilled Revenue			15,200,000	16,800,000
Due from PJM transmission settlement			2,400,000	$ 16,500,000
Refund of eligible excess ADIT and any related regulatory liability as required by the PUCO	$ 65,100,000
Refund of eligible excess ADIT and any related regulatory liability as required by the PUCO, including taxes			83,200,000
Reduction of Long-term regulatory liability related to deferred income taxes			$ 23.4