Industry Regulation - Rate Increases and Delivery Rate Percentages (Details) - Year 3 - USD ($) $ in Millions	Jun. 22, 2020	Jun. 15, 2016
NYSEG Electric
Public Utilities, General Disclosures [Line Items]
Rate Increase	$ 36.0	$ 30.0
Delivery Rate Increase	4.20%	4.10%
NYSEG Gas
Public Utilities, General Disclosures [Line Items]
Rate Increase	$ 3.0	$ 15.0
Delivery Rate Increase	1.60%	7.30%
RG&E Electric
Public Utilities, General Disclosures [Line Items]
Rate Increase	$ 16.0	$ 26.0
Delivery Rate Increase	3.30%	5.70%
RG&E Gas
Public Utilities, General Disclosures [Line Items]
Rate Increase	$ 2.0	$ 10.0
Delivery Rate Increase	1.30%	5.20%