Regulatory Matters - Summary of Utilities Rate Plans (O&R New York-Gas) (Details) - USD ($) $ in Millions	12 Months Ended				36 Months Ended
	Dec. 31, 2028	Dec. 31, 2027	Dec. 31, 2026	Dec. 31, 2024	Dec. 31, 2027	Dec. 31, 2024	Dec. 31, 2021	Dec. 31, 2023
Public Utilities, General Disclosures [Line Items]
Deferred regulatory assets				$ 848.0		$ 848.0		$ 722.0
O&R | Gas
Public Utilities, General Disclosures [Line Items]
Deferred regulatory assets				2.0		$ 2.0		$ 7.6
Deferrals for property taxes limitation from rates (percent)						90.00%
Recovery of late payment charges, amount				$ 0.6
Regulatory assets usefull life				15 years
Uncollecetible expenses, threshold amount				$ 0.5
Surcharge recovery threshold percentage				50.00%
O&R | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Authorized return on common equity (percent)		10.10%	10.10%
Common equity ratio (percent)	48.00%	48.00%	48.00%		48.00%
Requested rate increase (decrease), amount	$ 166.0	$ 266.0	$ 441.0
O&R | Gas | Rate Plan for Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes						$ 0.7
Amortization to income of net regulatory assets						0.8
Potential positive rate adjustment for gas safety and performance						1.2
Potential earnings adjustment mechanism incentives						$ 0.2
Authorized return on common equity (percent)				9.20%
Requested rate increase (decrease), amount							$ 4.4
Deferral, annual maximum (not more than) (percent)						0.10%
O&R | Gas | Rate Plan for Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes					$ 3.6
Amortization to income of net regulatory assets					$ 8.4
Authorized return on common equity (percent)					9.75%
O&R | Gas | Rate Plan for Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes						$ 7.4
Amortization to income of net regulatory assets						0.7
Potential positive rate adjustment for gas safety and performance						1.3
Potential earnings adjustment mechanism incentives						$ 0.2
Requested rate increase (decrease), amount							4.4
Deferral, annual maximum (not more than) (percent)						0.075%
O&R | Gas | Rate Plan for Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes					$ 18.0
Amortization to income of net regulatory assets					8.2
O&R | Gas | Rate Plan for Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes						$ 9.9
Amortization to income of net regulatory assets						0.3
Potential positive rate adjustment for gas safety and performance						1.4
Potential earnings adjustment mechanism incentives						$ 0.4
Requested rate increase (decrease), amount							$ 4.4
Deferral, annual maximum (not more than) (percent)						0.05%
O&R | Gas | Rate Plan for Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes					16.5
Amortization to income of net regulatory assets					$ 8.0
Energy Efficiency | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives						$ 0.2