Regulatory Matters - Summary of Utilities Rate Plans (O&R New York-Gas) (Details) - USD ($)	1 Months Ended	12 Months Ended					36 Months Ended
	Jan. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2024	Dec. 31, 2021
Public Utilities, General Disclosures [Line Items]
Deferred regulatory assets		$ 722,000,000	$ 702,000,000
O&R
Public Utilities, General Disclosures [Line Items]
Earnings above threshold		2,800,000	1,100,000	$ 1,700,000
O&R | Gas
Public Utilities, General Disclosures [Line Items]
Amount of revenues retained				4,000,000				$ 4,000,000
Share in variances in annual revenue retained (percent)								20.00%
Potential earnings adjustment mechanism incentives								$ 300,000
Deferred regulatory assets		7,600,000	2,000,000	4,000,000	$ 500,000	$ 800,000		4,000,000
Negative revenue adjustments		0	100,000	0	0	200,000
Cost reconciliation, deferred net regulatory liabilities		$ 12,100,000	3,400,000			6,000,000
Cost reconciliation, deferred net regulatory assets				$ 8,000,000	1,800,000			$ 8,000,000
Earnings sharing (percent)				9.60%				9.60%
Common equity ratio (percent)								48.00%
Recovery of late payment charges, period (in years)		3 years
Recovery of late payment charges, amount		$ 600,000
Recovery of late payment charges, return on equity threshold rate		0.05%
O&R | Gas | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Authorized return on common equity (percent)	10.25%
Common equity ratio (percent)	50.00%
Requested rate increase (decrease), amount	$ 14,400,000
O&R | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Earnings sharing (percent)							9.70%
Common equity ratio (percent)							48.00%
Deferrals for property taxes limitation from rates (percent)							90.00%
O&R | Gas | Customers
Public Utilities, General Disclosures [Line Items]
Share in variances in annual revenue retained (percent)								80.00%
O&R | Gas | Rate Plan for 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
Average rate base								593,000,000
Weighted average cost of capital (after-tax)								$ 454,000,000
Weighted average cost of capital (after-tax) (percent)								6.97%
Authorized return on common equity (percent)								9.00%
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 | Rate Plan for Year 1 | Scenario, Forecast
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
Potential positive rate adjustment for gas safety and performance							1,200,000
Average rate base							720,000,000
Weighted average cost of capital (after-tax)							$ 566,000,000
Weighted average cost of capital (after-tax) (percent)							6.77%
Authorized return on common equity (percent)							9.20%
Actual return on common equity (percent)							10.01%
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 | Rate Plan for Year 1 | AMI
Public Utilities, General Disclosures [Line Items]
Average rate base								20,000,000
O&R | Gas | Rate Plan for Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								5,500,000
O&R | Gas | Rate Plan for Year 1 | Maximum | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							$ 6,300,000
O&R | Gas | Rate Plan for 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
Average rate base								611,000,000
Weighted average cost of capital (after-tax)								$ 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 | Rate Plan for Year 2 | Scenario, Forecast
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
Potential positive rate adjustment for gas safety and performance							1,300,000
Average rate base							761,000,000
Weighted average cost of capital (after-tax)							$ 607,000,000
Weighted average cost of capital (after-tax) (percent)							6.73%
Actual return on common equity (percent)							10.40%
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 | Rate Plan for Year 2 | AMI
Public Utilities, General Disclosures [Line Items]
Average rate base								24,000,000
O&R | Gas | Rate Plan for Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								5,700,000
O&R | Gas | Rate Plan for Year 2 | Maximum | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							$ 6,700,000
O&R | Gas | Rate Plan for 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
Average rate base								632,000,000
Weighted average cost of capital (after-tax)								$ 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 | Rate Plan for Year 3 | Scenario, Forecast
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
Potential positive rate adjustment for gas safety and performance							1,400,000
Average rate base							803,000,000
Weighted average cost of capital (after-tax)							$ 694,000,000
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 | Rate Plan for Year 3 | AMI
Public Utilities, General Disclosures [Line Items]
Average rate base								25,000,000
O&R | Gas | Rate Plan for Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 6,000,000
O&R | Gas | Rate Plan for Year 3 | Maximum | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							$ 7,300,000
Energy Efficiency | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		$ 0	$ 200,000	$ 500,000	500,000	500,000
Service Termination | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		$ 200,000		200,000	$ 300,000	$ 700,000
Incentives reversed				$ 300,000