Regulatory Matters - Schedule of Utilities Rate Plans (CECONY-Steam) (Details) - CECONY - Steam	11 Months Ended	12 Months Ended											36 Months Ended
	Dec. 12, 2018 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 31, 2026 USD ($)	Dec. 31, 2016 USD ($)
Public Utilities, General Disclosures [Line Items]
Amortizations to income of net regulatory (assets) and liabilities														$ 37,000,000
Regulatory liabilities, amortization period										3 years				3 years
Negative revenue adjustments														$ 0
Regulatory reconciliations			$ 18,000,000				$ 8,000,000		$ 14,000,000	$ 8,000,000		$ 42,000,000		$ 8,000,000
Regulatory reconciliations				$ 11,000,000	$ 32,000,000	$ 35,000,000		$ 1,000,000			$ 17,000,000
Increase (decrease) in regulatory liabilities	$ 0			100,000			0		0	$ 0	0	100,000
Deferred regulatory asset (liability)			0		1,000,000	2,000,000
Authorized return on common equity														9.30%
Earnings sharing										9.90%				9.90%
Earnings sharing, threshold limit			$ 0	$ 0	$ 0	$ 0	$ 5,000,000	16,500,000	8,500,000	$ 7,800,000	$ 11,500,000	$ 0
Earnings sharing, positive adjustment								2,300,000	$ 1,100,000	4,000,000
Earnings sharing, additional adjustment								$ 200,000		400,000
Common equity ratio														48.00%
Revenue from contracts with customer, late payment charges, annual cap, percent (in percent)		0.005
Difference in property taxes (percent)		90.00%												90.00%
Deferral, annual maximum (not more than) (percent)														0.10%
Recovery deferral (percent)		80.00%
Maximum deferral (percent)		30.00%
Other regulatory liabilities										$ 8,000,000				$ 8,000,000
Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Authorized return on common equity													9.25%
Earnings sharing													9.75%
Common equity ratio													48.00%
Scenario, Forecast | Unprotected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA													$ 24,000,000
Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes														(22,400,000)
Average rate base														$ 1,511,000,000
Weighted average cost of capital (after-tax)														7.10%
Actual return on common equity, percent														9.82%
Cost of long-term debt										5.17%				5.17%
Late payment charges and fees		$ 2,500,000
Deferral, annual maximum (not more than) (percent)		0.10%
Year 1 | Production
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations														$ 1,752,000,000
Year 1 | Distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations														6,000,000
Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes													110,000,000
Amortizations to income of net regulatory (assets) and liabilities													15,000,000
Negative revenue adjustments													3,700,000
Regulatory reconciliations													7,000,000
Net utility plant reconciliations													2,025,000,000
Deferred regulatory asset (liability)													2,400,000
Average rate base													$ 1,799,000,000
Weighted average cost of capital (after-tax)													6.78%
Actual return on common equity, percent													6.55%
Cost of long-term debt													4.51%
Requested rate increase (decrease), amount													$ 77,800,000
Year 1 | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA													3,000,000
Tax cuts and jobs act of 2017, change in tax rate, regulatory asset, income tax benefit													11,000,000
Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes														19,800,000
Average rate base														$ 1,547,000,000
Weighted average cost of capital (after-tax)														7.13%
Actual return on common equity, percent														10.88%
Cost of long-term debt										5.23%				5.23%
Late payment charges and fees		$ 3,000,000.0
Deferral, annual maximum (not more than) (percent)		0.075%
Year 2 | Production
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations														$ 1,732,000,000
Year 2 | Distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations														11,000,000
Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes													44,000,000
Amortizations to income of net regulatory (assets) and liabilities													3,000,000
Negative revenue adjustments													3,800,000
Regulatory reconciliations													33,000,000
Net utility plant reconciliations													2,029,000,000
Deferred regulatory asset (liability)													4,000,000
Average rate base													$ 1,848,000,000
Weighted average cost of capital (after-tax)													6.81%
Actual return on common equity, percent													7.09%
Cost of long-term debt													4.58%
Requested rate increase (decrease), amount													$ 77,800,000
Year 2 | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA													5,000,000
Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes														20,300,000
Average rate base														$ 1,604,000,000
Weighted average cost of capital (after-tax)														7.21%
Actual return on common equity, percent														10.54%
Cost of long-term debt										5.39%				5.39%
Late payment charges and fees		$ 3,500,000
Deferral, annual maximum (not more than) (percent)		0.05%
Year 3 | Production
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations														$ 1,720,000,000
Year 3 | Distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations														25,000,000
Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Negative revenue adjustments														1,000,000
Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes													45,000,000
Amortizations to income of net regulatory (assets) and liabilities													3,000,000
Negative revenue adjustments													3,800,000
Net utility plant reconciliations													2,015,000,000
Average rate base													$ 1,882,000,000
Weighted average cost of capital (after-tax)													6.83%
Cost of long-term debt													4.62%
Requested rate increase (decrease), amount													$ 77,800,000
Year 3 | Scenario, Forecast | Protected Portion
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA													$ 6,000,000
Year 4
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														9.51%
Year 5
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														11.73%
Year 6
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														10.45%
Year 7
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														7.91%
Year 8
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														5.99%
Year 9
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														5.72%
Year 10
Public Utilities, General Disclosures [Line Items]
Base rate changes														$ 0
Actual return on common equity, percent														(0.10%)