Income Tax - Income Tax Reconciliation (Details)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
STATUTORY TAX RATE
Federal	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	4.00%	4.00%
Taxes attributable to non-controlling interest	(1.00%)	(1.00%)
Cost of removal	2.00%	1.00%
Other plant-related items	(1.00%)	0.00%
Renewable energy credits	(2.00%)	(1.00%)
CARES Act NOL carryback	(1.00%)	0.00%
Amortization of excess deferred federal income taxes	(9.00%)	(3.00%)
Other	(1.00%)	(1.00%)
Effective tax rate	12.00%	20.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	5.00%	5.00%
Taxes attributable to non-controlling interest	0.00%	0.00%
Cost of removal	2.00%	1.00%
Other plant-related items	(1.00%)	0.00%
Renewable energy credits	0.00%	0.00%
CARES Act NOL carryback	0.00%	0.00%
Amortization of excess deferred federal income taxes	(8.00%)	(3.00%)
Other	0.00%	(1.00%)
Effective tax rate	19.00%	23.00%

Effective Income Tax Rate Reconciliation, CARES Act Net Operating Loss Carryback, Percent

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Effective Income Tax Rate Reconciliation, Tax Credit, Renewable Energy Credits, Percent

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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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