Income Tax - Schedule of Income Tax Reconciliation (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]
Federal	35.00%	35.00%	35.00%
State income tax	5.00%	4.00%	4.00%
Cost of removal	(5.00%)	(5.00%)	(4.00%)
Manufacturing deduction		(1.00%)
Other	(1.00%)	(2.00%)	(1.00%)
Effective tax rate	34.00%	31.00%	34.00%
CECONY [Member]
Income Tax Contingency [Line Items]
Federal	35.00%	35.00%	35.00%
State income tax	5.00%	5.00%	4.00%
Cost of removal	(5.00%)	(5.00%)	(4.00%)
Other	(1.00%)	(1.00%)	(1.00%)
Effective tax rate	34.00%	34.00%	34.00%

Effective Income Tax Rate Reconciliation, cost of removal

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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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-Publisher FASB

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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 deduction for qualified production activity.

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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 applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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