Income Tax - Income Tax Reconciliation (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
STATUTORY TAX RATE
Federal	21.00%	21.00%	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	4.00%	5.00%	4.00%	5.00%
Cost of removal			1.00%	1.00%
Other plant-related items	0.00%	(1.00%)	0.00%	(1.00%)
Renewable energy credits	(1.00%)	(1.00%)	(2.00%)	(1.00%)
TCJA deferred tax re-measurement	0	0.07	0	0.03
Reserve for uncertain tax positions	1.00%	0.00%
Amortization of excess deferred federal income taxes	(3.00%)	(2.00%)	(4.00%)	(3.00%)
Prior period return adjustments	(2.00%)	0.00%
Other	0.00%	(1.00%)	(1.00%)	(1.00%)
Effective tax rate	20.00%	28.00%	19.00%	24.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	21.00%	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	5.00%	5.00%	5.00%	5.00%
Cost of removal			1.00%	1.00%
Other plant-related items	0.00%	(1.00%)	(1.00%)	(1.00%)
Renewable energy credits	0.00%	0.00%	0.00%	0.00%
TCJA deferred tax re-measurement	0	0	0	0
Reserve for uncertain tax positions	0.00%	0.00%
Amortization of excess deferred federal income taxes	(3.00%)	(2.00%)	(3.00%)	(3.00%)
Prior period return adjustments	0.00%	0.00%
Other	(1.00%)	(1.00%)	(1.00%)	(1.00%)
Effective tax rate	22.00%	22.00%	22.00%	22.00%

Effective Income Tax Rate Reconciliation, cost of removal

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Effective Income Tax Rate Reconciliation, Other Plant-Related Items, 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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Percentage of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to Tax Cuts and Jobs Act.

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