Income Tax - Income Tax Reconciliation (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
STATUTORY TAX RATE
Federal	21.00%	21.00%	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	3.00%	5.00%	4.00%	5.00%
Cost of removal	2.00%	2.00%	1.00%	1.00%
Other plant-related items	(2.00%)	(1.00%)	(1.00%)	(1.00%)
Renewable energy credits	(5.00%)	(3.00%)	(2.00%)	(2.00%)
Reserve for uncertain tax positions	2.00%	0.00%
Amortization of excess deferred federal income taxes	(10.00%)	(7.00%)	(5.00%)	(4.00%)
Other	0.00%	0.00%
Effective tax rate	11.00%	17.00%	18.00%	20.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	21.00%	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	3.00%	4.00%	4.00%	5.00%
Cost of removal	2.00%	2.00%	1.00%	1.00%
Other plant-related items	(1.00%)	(1.00%)	(1.00%)	(1.00%)
Renewable energy credits	0.00%	0.00%	0.00%	0.00%
Reserve for uncertain tax positions	0.00%	0.00%
Amortization of excess deferred federal income taxes	(9.00%)	(8.00%)	(4.00%)	(4.00%)
Other	(1.00%)	(1.00%)
Effective tax rate	15.00%	17.00%	21.00%	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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