Income Tax - Schedule of Income Tax Reconciliation (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
STATUTORY TAX RATE
Federal	21.00%	21.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	4.00%	4.00%
Taxes attributable to noncontrolling interests	(1.00%)	0.00%	0.00%
Cost of removal	1.00%	1.00%	1.00%
Other plant-related items	(1.00%)	(1.00%)	(1.00%)
TCJA deferred tax re-measurement	0	0.02	(0.13)
Amortization of excess deferred federal income taxes	(4.00%)	(3.00%)	0.00%
Renewable energy credits	(2.00%)	(1.00%)	(1.00%)
Research and development credits	(1.00%)	0.00%	0.00%
Other	0.00%	0.00%	(2.00%)
Effective tax rate	17.00%	23.00%	23.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	21.00%	35.00%
Changes in computed taxes resulting from:
State income tax	5.00%	5.00%	4.00%
Taxes attributable to noncontrolling interests	0.00%	0.00%	0.00%
Cost of removal	1.00%	1.00%	1.00%
Other plant-related items	(1.00%)	(1.00%)	(1.00%)
TCJA deferred tax re-measurement	0	0	0
Amortization of excess deferred federal income taxes	(4.00%)	(3.00%)	0.00%
Renewable energy credits	0.00%	0.00%	0.00%
Research and development credits	(1.00%)	(1.00%)	0.00%
Other	0.00%	(1.00%)	(1.00%)
Effective tax rate	21.00%	21.00%	38.00%

Effective Income Tax Rate Reconciliation, cost of removal

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Federal Statutory Income Tax Rate [Abstract]

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to noncontrolling interest income (loss) exempt from income taxes.

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