Regulatory Matters - Rate Plans (Details) - O&R - NYSPSC - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2018	May 31, 2018
Electric
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount		$ 10.6
Increase (decrease) in requested rate increase	$ 30.4
Authorized return on common equity, percentage	9.75%	8.60%
Gas
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount		$ (6.7)
Increase (decrease) in requested rate increase	$ (0.5)
Authorized return on common equity, percentage	9.75%	8.60%