Regulatory Matters (Details) $ in Millions	3 Months Ended
	Dec. 31, 2018 USD ($)
Regulatory Matters [Line Items]
Required Temporary Refund on Customer Rates	2.20%
Approved Return on Equity	8.70%
Empire [Member]
Regulatory Matters [Line Items]
Estimated Increase to Revenues from Interim Rates	$ 4.6
Empire [Member] | Maximum [Member]
Regulatory Matters [Line Items]
Revenue Sharing Mechanism Percentage	55.00%
Revenue Sharing Mechanism Revenue Level	$ 68.4
Empire [Member] | Minimum [Member]
Regulatory Matters [Line Items]
Revenue Sharing Mechanism Percentage	35.00%
Revenue Sharing Mechanism Revenue Level	$ 64.4
PENNSYLVANIA | 2017 Tax Reform Act Regulatory Refund [Member]
Regulatory Matters [Line Items]
Refund Provision Associated with Impact of 2017 Tax Reform	4.4
NEW YORK | 2017 Tax Reform Act Regulatory Refund [Member]
Regulatory Matters [Line Items]
Refund Provision Associated with Impact of 2017 Tax Reform	$ 8.6