Regulatory Matters (Details) - USD ($) $ in Millions	Mar. 01, 2019	Jan. 22, 2019	Jan. 01, 2018	Mar. 31, 2019	Dec. 31, 2018
Requested Distribution Modernization Rider annual revenue through filing		$ 199.0
Regulatory Assets, Noncurrent				$ 151.2	$ 152.6
Unbilled Revenue				15.7	16.8
Period for refund of eligible excess ADIT and any related regulatory liability as required by PUCO			10 years
Due from PJM transmission settlement				9.8	16.5
Refund of eligible excess ADIT and any related regulatory liability as required by the PUCO	$ 65.1
Subsidiaries [Member]
Requested Distribution Modernization Rider annual revenue through filing		$ 199.0
Regulatory Assets, Noncurrent				151.2	152.6
Unbilled Revenue				15.7	16.8
Period for refund of eligible excess ADIT and any related regulatory liability as required by PUCO			10 years
Due from PJM transmission settlement				$ 9.8	$ 16.5
Refund of eligible excess ADIT and any related regulatory liability as required by the PUCO	$ 65.1