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, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2021	Oct. 31, 2018	Dec. 31, 2022	Dec. 31, 2015
Public Utilities, General Disclosures [Line Items]
Deferred revenues		$ 599,000,000	$ 599,000,000
Deferred revenues		$ 41,000,000	17,000,000	$ 20,000,000	$ 87,000,000
NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%
Percentage of debt to total consolidated debt		20.00%
Maximum | NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%
O&R
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		$ 3,000,000
O&R | Gas
Public Utilities, General Disclosures [Line Items]
Deferred revenues		500,000	800,000			$ 800,000
Deferred revenues			6,300,000	1,700,000	6,200,000
Negative revenue adjustments		200,000	100,000	0	0	0
Cost reconciliation, deferred net regulatory liabilities		1,800,000	6,000,000	7,400,000	3,500,000					$ 4,500,000
Cost reconciliation, deferred net regulatory assets						$ 6,600,000
Deferred regulatory asset (liability)			(400,000)
Authorized return on common equity (percent)								9.00%
Earnings sharing (percent)								9.60%
Earnings sharing, threshold limit				$ 200,000	$ 4,000,000
Common Equity Ratio, Percentage								4800.00%
O&R | Gas | NYSPSC | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Common Equity Ratio, Percentage	50.00%
Requested rate increase (decrease), amount	$ 9,800,000
Return on common equity (percent)	9.50%
O&R | Gas | Property Tax and Interest Rate Reconciliations
Public Utilities, General Disclosures [Line Items]
Regulatory assets not recoverable								$ 14,000,000
O&R | Gas | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Amount of revenues retained									$ 4,000,000.0
Share in variances in annual revenue retained (percent)							20.00%
Potential earnings adjustment mechanism incentives							$ 300,000
Authorized return on common equity (percent)							9.00%
Earnings sharing (percent)									9.60%
Common Equity Ratio, Percentage							4800.00%
O&R | Gas | Scenario, Forecast | Customers
Public Utilities, General Disclosures [Line Items]
Share in variances in annual revenue retained (percent)							80.00%
O&R | Gas | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes								16,400,000
Amortization to income of net regulatory assets								1,700,000
Net utility plant reconciliations								492,000,000
Average rate base								$ 366,000,000
Weighted average cost of capital (after-tax) (percent)								7.10%
Actual return on common equity (percent)								11.20%
Cost of long-term debt (percent)								5.42%
Rate exclusion amount with balance below regulatory threshold								$ 500,000
O&R | Gas | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								3,700,000
O&R | Gas | Year 1 | Scenario, Forecast
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 | Scenario, Forecast | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							20,000,000
O&R | Gas | Year 1 | Scenario, Forecast | 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								16,400,000
Amortization to income of net regulatory assets								2,100,000
Net utility plant reconciliations								518,000,000
Average rate base								$ 391,000,000
Weighted average cost of capital (after-tax) (percent)								7.06%
Actual return on common equity (percent)								9.70%
Cost of long-term debt (percent)								5.35%
Rate exclusion amount with balance below regulatory threshold								$ 4,200,000
O&R | Gas | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								4,700,000
O&R | Gas | Year 2 | Scenario, Forecast
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							$ 1,000,000.0
O&R | Gas | Year 2 | Scenario, Forecast | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							24,000,000
O&R | Gas | Year 2 | Scenario, Forecast | 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								5,800,000
Base rate change through surcharge								10,600,000
Amortization to income of net regulatory assets								2,500,000
Net utility plant reconciliations								546,000,000
Average rate base								$ 417,000,000
Weighted average cost of capital (after-tax) (percent)								7.06%
Actual return on common equity (percent)								8.10%
Cost of long-term debt (percent)								5.35%
Rate exclusion amount with balance below regulatory threshold								$ 7,200,000
O&R | Gas | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 4,900,000
O&R | Gas | Year 3 | Scenario, Forecast
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%
Cost of long-term debt (percent)							5.14%
Requested rate increase (decrease), amount							$ 1,000,000.0
O&R | Gas | Year 3 | Scenario, Forecast | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							25,000,000
O&R | Gas | Year 3 | Scenario, Forecast | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							$ 6,000,000.0
Energy Efficiency | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		300,000
Service Termination | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		$ 500,000	$ 700,000