Regulatory Matters - Summary of Utilities Rate Plans (O&R New York-Electric) (Details) - USD ($)	1 Months Ended	12 Months Ended						24 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, 2015	Oct. 31, 2017	Dec. 31, 2021	Oct. 31, 2018	Dec. 31, 2022
Public Utilities, General Disclosures [Line Items]
Deferred revenues		$ 41,000,000	$ 17,000,000	$ 20,000,000	$ 87,000,000
Deferred revenues		$ 599,000,000	599,000,000
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 | Electric
Public Utilities, General Disclosures [Line Items]
Deferred revenues						$ 6,300,000
Deferred revenues		6,000,000	100,000	500,000	11,200,000
Negative revenue adjustments			0	0	0	1,250,000
Deferral of net increase (decrease) to regulatory assets		30,300,000	4,300,000	5,000,000	3,200,000	7,400,000	$ 300,000
Net utility plant reconciliations			1,400,000	(1,900,000)	(1,900,000)	2,200,000
Authorized return on common equity (percent)								900.00%
Earnings sharing (percent)								9.60%
Earnings sharing, threshold limit				300,000	6,100,000
Common Equity Ratio, Percentage								4800.00%
Deferred storm and property reserve deficiency, noncurrent								$ 59,300,000
Deferred storm and property reserve deficiency, recovery period								5 years
Deferred storm and property reserve deficiency not recovered								$ 1,000,000
Deferred Regulatory Asset (Liability)		400,000
O&R | Electric | NYSPSC | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Common Equity Ratio, Percentage	50.00%
Requested rate increase (decrease), amount	$ 24,500,000
Return on common equity (percent)	9.50%
O&R | Electric | Property Tax and Interest Rate Reconciliations
Public Utilities, General Disclosures [Line Items]
Regulatory assets not recoverable								4,000,000
O&R | Electric | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes								9,300,000
Amortization to income of net regulatory assets								(8,500,000)
Net utility plant reconciliations								928,000,000
Average rate base								$ 763,000,000
Weighted average cost of capital (after-tax) (percent)								7.10%
Actual return on common equity (percent)								10.80%
Cost of long-term debt (percent)								5.42%
Deferred storm and property reserve deficiency, noncurrent								$ 11,850,000
Rate exclusion amount with balance below regulatory threshold								1,000,000
O&R | Electric | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								4,000,000
O&R | Electric | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes								8,800,000
Amortization to income of net regulatory assets								(9,400,000)
Net utility plant reconciliations								970,000,000
Average rate base								$ 805,000,000
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								$ 9,000,000
O&R | Electric | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								4,000,000
O&R | Electric | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes								0
Amortization to income of net regulatory assets								0
Average rate base								$ 805,000,000
Weighted average cost of capital (after-tax) (percent)								7.06%
Actual return on common equity (percent)								7.20%
Cost of long-term debt (percent)								5.35%
O&R | Electric | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 4,000,000
O&R | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Authorized return on common equity (percent)									900.00%
Earnings sharing (percent)											9.60%
Common Equity Ratio, Percentage									4800.00%
Deferrals for property taxes limitation from rates (percent)									90.00%
O&R | Electric | Scenario, Forecast | 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 | Scenario, Forecast | Year 1 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									$ 1,008,000,000
O&R | Electric | Scenario, Forecast | Year 1 | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									48,000,000
O&R | Electric | Scenario, Forecast | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)									4,400,000
O&R | Electric | Scenario, Forecast | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes									8,000,000.0
Amortization to income of net regulatory assets									(1,500,000)
Potential earnings adjustment mechanism incentives									4,000,000.0
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 | Scenario, Forecast | Year 2 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									$ 1,032,000,000
O&R | Electric | Scenario, Forecast | Year 2 | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									58,000,000
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									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%
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 | Scenario, Forecast | Year 3 | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									$ 1,083,000,000
O&R | Electric | Scenario, Forecast | Year 3 | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									61,000,000
O&R | Electric | Scenario, Forecast | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)									4,500,000
O&R | Gas
Public Utilities, General Disclosures [Line Items]
Deferred revenues			6,300,000	1,700,000	6,200,000
Deferred revenues		500,000	800,000			800,000
Negative revenue adjustments		200,000	100,000	0	0	$ 0
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%
Deferred Regulatory Asset (Liability)			400,000
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 | 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 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 3
Public Utilities, General Disclosures [Line Items]
Base rate changes										5,800,000
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 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
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 | 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 | Scenario, Forecast | Year 1 | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									20,000,000
O&R | Gas | Scenario, Forecast | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)									5,500,000
O&R | Gas | Scenario, Forecast | 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									$ 1,000,000.0
O&R | Gas | Scenario, Forecast | Year 2 | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									24,000,000
O&R | Gas | Scenario, Forecast | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)									5,700,000
O&R | Gas | Scenario, Forecast | 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%
Cost of long-term debt (percent)									5.14%
Requested rate increase (decrease), amount									$ 1,000,000.0
O&R | Gas | Scenario, Forecast | Year 3 | AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations									25,000,000
O&R | Gas | Scenario, Forecast | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)									$ 6,000,000.0
Energy Efficiency | O&R | Electric
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		2,600,000
Energy Efficiency | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		300,000
Service Termination | O&R | Electric
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		500,000	200,000
Service Termination | O&R | Gas
Public Utilities, General Disclosures [Line Items]
Actual earnings adjustment mechanism incentives		$ 500,000	$ 700,000