Income Tax - Schedule of Income Tax Reconciliation (Details)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
STATUTORY TAX RATE
Federal	35.00%	35.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	5.00%	5.00%
Cost of removal	(1.00%)	(5.00%)	(5.00%)
Renewable energy credits	(1.00%)	(1.00%)	(0.00%)
Research and development credits	(1.00%)	0.00%	0.00%
Other	0.00%	0.00%	(1.00%)
Effective tax rate	36.00%	34.00%	34.00%
CECONY
STATUTORY TAX RATE
Federal	35.00%	35.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	5.00%	5.00%
Cost of removal	(1.00%)	(5.00%)	(5.00%)
Renewable energy credits	(0.00%)	(0.00%)	(0.00%)
Research and development credits	(1.00%)	0.00%	0.00%
Other	(1.00%)	0.00%	(1.00%)
Effective tax rate	36.00%	35.00%	34.00%

Effective Income Tax Rate Reconciliation, cost of removal

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32698-109319

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 12
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32687-109319

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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-Section S99
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-Name Accounting Standards Codification
-Topic 740
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-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32698-109319

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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 other adjustments.

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