Income Tax - Income Tax Reconciliation (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
STATUTORY TAX RATE
Federal	21.00%	21.00%	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	6.00%	6.00%	5.00%	5.00%
Amortization of excess deferred federal income taxes	(20.00%)	(9.00%)	(12.00%)	(4.00%)
Taxes attributable to non-controlling interest	(2.00%)	(4.00%)	(1.00%)	(1.00%)
Cost of removal	4.00%	2.00%	2.00%	1.00%
Other plant-related items	(3.00%)	(1.00%)	(2.00%)	(1.00%)
Allowance for uncollectible accounts	1.00%	0.00%
Renewable energy credits	(4.00%)	(4.00%)	(3.00%)	(2.00%)
Amortization of excess deferred state income taxes	0.00%	(2.00%)	0.00%	(1.00%)
CARES Act NOL carryback			(1.00%)	0.00%
Other	1.00%	1.00%	1.00%	(1.00%)
Effective tax rate	4.00%	10.00%	10.00%	17.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	21.00%	21.00%	21.00%
Changes in computed taxes resulting from:
State income tax	6.00%	5.00%	5.00%	5.00%
Amortization of excess deferred federal income taxes	(25.00%)	(9.00%)	(12.00%)	(4.00%)
Taxes attributable to non-controlling interest	0.00%	0.00%	0.00%	0.00%
Cost of removal	5.00%	2.00%	2.00%	1.00%
Other plant-related items	(4.00%)	(1.00%)	(2.00%)	0.00%
Allowance for uncollectible accounts	1.00%	0.00%
Renewable energy credits	0.00%	0.00%	0.00%	0.00%
Amortization of excess deferred state income taxes	0.00%	(2.00%)	0.00%	(1.00%)
CARES Act NOL carryback			0.00%	0.00%
Other	0.00%	(1.00%)	1.00%	(1.00%)
Effective tax rate	4.00%	15.00%	15.00%	21.00%

Effective Income Tax Rate Reconciliation, Allowance For Uncollectible Accounts, Percent

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

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Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization Of Excess Deferred Federal Income Taxes, Percent

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Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization Of Excess Deferred State Income Taxes, Percent

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Effective Income Tax Rate Reconciliation, Other Plant-Related Items, 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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