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Percentage of public utility's requested rate increase (decrease) with regulatory agency.

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Regulatory Matters - Pennsylvania and West Virginia (Details) $ in Millions							1 Months Ended	6 Months Ended		9 Months Ended
	Aug. 31, 2018 USD ($)	May 30, 2018 USD ($)	Mar. 09, 2018 USD ($)	Jun. 14, 2017 USD ($)	Jan. 19, 2017 USD ($)	Jun. 19, 2015	Mar. 31, 2016 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 proposal
Pennsylvania \| DSP June 2017- May 2019
Regulatory Matters [Line Items]
Number of RFP's \| proposal										1
RFP term										2 years
Pennsylvania \| DSP June 2019- May 2023
Regulatory Matters [Line Items]
Number of RFP's \| proposal										2
RFP term										2 years
Pennsylvania \| Three Month Period \| DSP June 2019- May 2023
Regulatory Matters [Line Items]
Term of energy contract										3 months
Pennsylvania \| Twelve month period \| DSP June 2017- May 2019
Regulatory Matters [Line Items]
Term of energy contract										12 months
Pennsylvania \| Twelve month period \| DSP June 2019- May 2023
Regulatory Matters [Line Items]
Term of energy contract										12 months
Pennsylvania \| Twenty-four month period \| DSP June 2017- May 2019
Regulatory Matters [Line Items]
Term of energy contract										24 months
Pennsylvania \| Twenty-four month period \| DSP June 2019- May 2023
Regulatory Matters [Line Items]
Term of energy contract										24 months
Pennsylvania \| Pennsylvania Companies \| PPUC \| EE&C Phase III
Regulatory Matters [Line Items]
Approved amount of annual increase							$ (390.0)
Pennsylvania \| ME
Regulatory Matters [Line Items]
Approved amount of annual increase					$ (96.0)
Pennsylvania \| ME \| PPUC
Regulatory Matters [Line Items]
Demand reduction targets proposed						1.80%
Energy consumption reduction targets proposed						4.00%
Amount of requested rate increase (decrease)				$ (51.3)
Net annual effect on rates			$ 37.0
Pennsylvania \| Penn
Regulatory Matters [Line Items]
Approved amount of annual increase					(29.0)
Pennsylvania \| Penn \| PPUC
Regulatory Matters [Line Items]
Demand reduction targets proposed						1.70%
Energy consumption reduction targets proposed						3.30%
Amount of requested rate increase (decrease)				(33.2)
Net annual effect on rates			9.0
Pennsylvania \| WP
Regulatory Matters [Line Items]
Approved amount of annual increase					(66.0)
Pennsylvania \| WP \| PPUC
Regulatory Matters [Line Items]
Demand reduction targets proposed						1.80%
Energy consumption reduction targets proposed						2.60%
Amount of requested rate increase (decrease)				(50.1)
Net annual effect on rates			30.0
Pennsylvania \| PN
Regulatory Matters [Line Items]
Approved amount of annual increase					$ (100.0)
Pennsylvania \| PN \| PPUC
Regulatory Matters [Line Items]
Demand reduction targets proposed						0.00%
Energy consumption reduction targets proposed						3.90%
Amount of requested rate increase (decrease)				$ (44.8)
Net annual effect on rates			$ 40.0
West Virginia \| MP and PE \| WVPSC
Regulatory Matters [Line Items]
Net annual effect on rates		$ 26.2
West Virginia \| MP and PE \| WVPSC \| ENEC
Regulatory Matters [Line Items]
Amount of requested rate increase (decrease)	$ (100.9)
Net annual effect on rates	25.6
West Virginia \| MP and PE \| WVPSC \| Elimination of Energy Efficiency Cost Rate Surcharge
Regulatory Matters [Line Items]
Amount of requested rate increase (decrease)	$ (2.1)
Requested rate decrease (percentage)	(7.20%)
Scenario, Forecast \| Pennsylvania \| PPUC \| Temporary Rates Order Tracked Value
Regulatory Matters [Line Items]
Rate filing period								3 years
Scenario, Forecast \| Pennsylvania \| ME \| PPUC \| Temporary Rates Order
Regulatory Matters [Line Items]
Approved amount of annual increase									$ (19.0)
Rate filing period									6 months
Scenario, Forecast \| Pennsylvania \| ME \| PPUC \| Temporary Rates Order Tracked Value
Regulatory Matters [Line Items]
Approved amount of annual increase								$ 12.0
Scenario, Forecast \| Pennsylvania \| Penn \| PPUC \| Temporary Rates Order
Regulatory Matters [Line Items]
Approved amount of annual increase									$ (5.0)
Scenario, Forecast \| Pennsylvania \| Penn \| PPUC \| Temporary Rates Order Tracked Value
Regulatory Matters [Line Items]
Approved amount of annual increase								3.0
Scenario, Forecast \| Pennsylvania \| WP \| PPUC \| Temporary Rates Order
Regulatory Matters [Line Items]
Approved amount of annual increase									(15.0)
Scenario, Forecast \| Pennsylvania \| WP \| PPUC \| Temporary Rates Order Tracked Value
Regulatory Matters [Line Items]
Approved amount of annual increase								10.0
Scenario, Forecast \| Pennsylvania \| PN \| PPUC \| Temporary Rates Order
Regulatory Matters [Line Items]
Approved amount of annual increase									$ (20.0)
Scenario, Forecast \| Pennsylvania \| PN \| PPUC \| Temporary Rates Order Tracked Value
Regulatory Matters [Line Items]
Approved amount of annual increase								$ 13.0