Summary of Significant Accounting Policies and Other Matters - Plant and Depreciation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated amortization	$ 297	$ 228
Annual aggregate depreciation allowance	1,802
Prepayments	16	12
Other deferred charges and noncurrent assets	81	54
Depreciation expense, other deferred charges and noncurrent assets and prepayments	12	7
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	22	10
Software Licenses
Public Utility, Property, Plant and Equipment [Line Items]
Gross asset	79	86
Estimated aggregate annual amortization expense	7
Accumulated amortization	$ 24	$ 17
Non-Utility Plant | Maximum | Land And Conduit
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	10 years
Non-Utility Plant | Maximum | Wind Power Generating Assets
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	30 years
Non-Utility Plant | Maximum | Solar Powered Generating Assets
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	35 years
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
AFUDC rates (percent)	4.50%	5.20%	5.10%
Average depreciation rates (percent)	3.50%	3.50%	3.20%
Annual aggregate depreciation allowance	$ 1,710
Prepayments	15	$ 11
Other deferred charges and noncurrent assets	78	51
Depreciation expense, other deferred charges and noncurrent assets and prepayments	11	6
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	19	8
CECONY | Software Licenses
Public Utility, Property, Plant and Equipment [Line Items]
Gross asset	74	81
Estimated aggregate annual amortization expense	7
Accumulated amortization	$ 24	$ 17
CECONY | Electric | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | Electric | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	85 years
CECONY | Gas | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | Gas | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	90 years
CECONY | Steam | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | Steam | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	80 years
CECONY | General Plant | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | General Plant | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	55 years
O&R
Public Utility, Property, Plant and Equipment [Line Items]
AFUDC rates (percent)	4.80%	5.30%	5.30%
Average depreciation rates (percent)	3.10%	3.20%	3.00%
O&R | Electric | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
O&R | Electric | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	75 years
O&R | General Plant | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
O&R | General Plant | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	50 years