Regulatory Matters - Summary of Utilities Rate Plans (O&R New York-Electric) (Details) - USD ($)	1 Months Ended	12 Months Ended			36 Months Ended
	Oct. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2024	Dec. 31, 2021	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Deferred revenues		$ 662,000,000	$ 599,000,000			$ 662,000,000
Deferred revenues		$ 7,000,000	41,000,000	$ 17,000,000		$ 7,000,000	$ 20,000,000
NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%				15.00%
Percentage of debt to total consolidated debt		20.00%				20.00%
Maximum | NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%				15.00%
O&R | Electric
Public Utilities, General Disclosures [Line Items]
Deferred revenues			6,000,000	100,000
Deferred revenues		$ 10,000,000				$ 10,000,000
Negative revenue adjustments		0	0	0
Deferral of net increase (decrease) to regulatory assets		$ 24,000,000	30,300,000	4,300,000
Deferred regulatory asset (liability)			(400,000)
Earnings sharing (percent)		9.60%				9.60%
Common equity ratio, percentage						48.00%
Deferrals for property taxes limitation from rates (percent)						90.00%
O&R | Electric | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes						$ 13,400,000
Amortization to income of net regulatory assets						(1,500,000)
Potential earnings adjustment mechanism incentives						3,600,000
Potential incentive if target is met, related to service terminations						500,000
Average rate base						$ 878,000,000
Weighted average cost of capital (after-tax) (percent)						6.97%
Actual return on common equity (percent)						9.60%
Cost of long-term debt (percent)						5.17%
Requested rate increase (decrease), amount						$ 8,600,000
Deferral, annual maximum (not more than) (percent)						10.00%
O&R | Electric | Year 1 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						$ 1,008,000,000
O&R | Electric | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						4,400,000
O&R | Electric | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes						8,000,000
Amortization to income of net regulatory assets						(1,500,000)
Potential earnings adjustment mechanism incentives						4,000,000
Potential incentive if target is met, related to service terminations						500,000
Average rate base						$ 906,000,000
Weighted average cost of capital (after-tax) (percent)						6.96%
Actual return on common equity (percent)						8.76%
Cost of long-term debt (percent)						5.14%
Requested rate increase (decrease), amount						$ 12,100,000
Deferral, annual maximum (not more than) (percent)						7.50%
O&R | Electric | Year 2 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						$ 1,032,000,000
O&R | Electric | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						4,400,000
O&R | Electric | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes						5,800,000
Amortization to income of net regulatory assets						(1,500,000)
Potential earnings adjustment mechanism incentives						4,200,000
Potential incentive if target is met, related to service terminations						500,000
Average rate base						$ 948,000,000
Weighted average cost of capital (after-tax) (percent)						6.96%
Actual return on common equity (percent)						9.16%
Cost of long-term debt (percent)						5.14%
Requested rate increase (decrease), amount						$ 12,200,000
Deferral, annual maximum (not more than) (percent)						5.00%
O&R | Electric | Year 3 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations						$ 1,083,000,000
O&R | Electric | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						4,500,000
O&R | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Earnings sharing (percent)					9.70%
O&R | Electric | Scenario, Forecast | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes					$ 4,900,000
Amortization to income of net regulatory assets					(11,800,000)
Potential earnings adjustment mechanism incentives					3,300,000
Net utility plant reconciliations					1,175,000,000
Average rate base					$ 1,021,000,000
Weighted average cost of capital (after-tax) (percent)					6.77%
Cost of long-term debt (percent)					4.58%
Requested rate increase (decrease), amount					$ 11,700,000
O&R | Electric | Scenario, Forecast | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					4,300,000
O&R | Electric | Scenario, Forecast | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes					16,200,000
Amortization to income of net regulatory assets					(13,500,000)
Potential earnings adjustment mechanism incentives					2,300,000
Net utility plant reconciliations					1,198,000,000
Average rate base					$ 1,044,000,000
Weighted average cost of capital (after-tax) (percent)					6.73%
Cost of long-term debt (percent)					4.51%
Requested rate increase (decrease), amount					$ 11,700,000
O&R | Electric | Scenario, Forecast | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					4,400,000
O&R | Electric | Scenario, Forecast | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes					23,100,000
Amortization to income of net regulatory assets					(15,200,000)
Potential earnings adjustment mechanism incentives					4,000,000.0
Net utility plant reconciliations					1,304,000,000
Average rate base					$ 1,144,000,000
Weighted average cost of capital (after-tax) (percent)					6.72%
Cost of long-term debt (percent)					4.49%
Requested rate increase (decrease), amount					$ 11,700,000
O&R | Electric | Scenario, Forecast | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					$ 5,100,000
O&R | Gas
Public Utilities, General Disclosures [Line Items]
Potential earnings adjustment mechanism incentives						300,000
Deferred revenues		$ 4,000,000	500,000	800,000		$ 4,000,000
Negative revenue adjustments				200,000
Earnings sharing (percent)		9.60%				9.60%
Common equity ratio, percentage						48.00%
O&R | Gas | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes						$ (7,500,000)
Amortization to income of net regulatory assets						(1,800,000)
Potential earnings adjustment mechanism incentives						1,200,000
Net utility plant reconciliations						593,000,000
Average rate base						$ 454,000,000
Weighted average cost of capital (after-tax) (percent)						6.97%
Actual return on common equity (percent)						8.90%
Cost of long-term debt (percent)						5.17%
Requested rate increase (decrease), amount						$ (5,900,000)
O&R | Gas | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						5,500,000
O&R | Gas | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes						3,600,000
Amortization to income of net regulatory assets						(1,800,000)
Potential earnings adjustment mechanism incentives						1,300,000
Net utility plant reconciliations						611,000,000
Average rate base						$ 476,000,000
Weighted average cost of capital (after-tax) (percent)						6.96%
Actual return on common equity (percent)						9.58%
Cost of long-term debt (percent)						5.14%
Requested rate increase (decrease), amount						$ 1,000,000
O&R | Gas | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						5,700,000
O&R | Gas | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes						700,000
Amortization to income of net regulatory assets						(1,800,000)
Potential earnings adjustment mechanism incentives						1,300,000
Net utility plant reconciliations						632,000,000
Average rate base						$ 498,000,000
Weighted average cost of capital (after-tax) (percent)						6.96%
Actual return on common equity (percent)						10.11%
Cost of long-term debt (percent)						5.14%
Requested rate increase (decrease), amount						$ 1,000,000
O&R | Gas | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)						$ 6,000,000
O&R | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Earnings sharing (percent)					9.70%
Deferrals for property taxes limitation from rates (percent)					90.00%
O&R | Gas | Scenario, Forecast | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes					$ 700,000
Amortization to income of net regulatory assets					(800,000)
Potential earnings adjustment mechanism incentives					200,000
Net utility plant reconciliations					720,000,000
Average rate base					$ 566,000,000
Weighted average cost of capital (after-tax) (percent)					6.77%
Cost of long-term debt (percent)					4.58%
Requested rate increase (decrease), amount					$ 4,400,000
Deferral, annual maximum (not more than) (percent)					0.10%
O&R | Gas | Scenario, Forecast | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					$ 6,300,000
O&R | Gas | Scenario, Forecast | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes					7,400,000
Amortization to income of net regulatory assets					(700,000)
Potential earnings adjustment mechanism incentives					200,000
Net utility plant reconciliations					761,000,000
Average rate base					$ 607,000,000
Weighted average cost of capital (after-tax) (percent)					6.73%
Cost of long-term debt (percent)					4.51%
Requested rate increase (decrease), amount					$ 4,400,000
Deferral, annual maximum (not more than) (percent)					0.075%
O&R | Gas | Scenario, Forecast | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					$ 6,700,000
O&R | Gas | Scenario, Forecast | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes					9,900,000
Amortization to income of net regulatory assets					(300,000)
Potential earnings adjustment mechanism incentives					400,000
Net utility plant reconciliations					803,000,000
Average rate base					$ 649,000,000
Weighted average cost of capital (after-tax) (percent)					6.72%
Cost of long-term debt (percent)					4.49%
Requested rate increase (decrease), amount					$ 4,400,000
Deferral, annual maximum (not more than) (percent)					0.05%
O&R | Gas | Scenario, Forecast | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					$ 7,300,000
O&R | Electric and Gas Transmission Projects
Public Utilities, General Disclosures [Line Items]
Recovery of late payment charges, period	3 years
Recovery of late payment charges, amount	$ 2,800,000
Recovery of late payment charges, return on equity threshold rate	0.05%
Energy Efficiency | O&R | Electric
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		$ 1,800,000	1,900,000	2,600,000
Energy Efficiency | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		500,000
Service Termination | O&R | Electric
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		0	500,000	200,000
Incentives reversed		500,000
Service Termination | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		200,000	$ 300,000	$ 700,000
Incentives reversed		$ 300,000