Stock-Based Compensation - Summary of Changes in Status of Performance RSUs' (Detail) - Performance-Based Restricted Stock	12 Months Ended
Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested Units, Beginning Balance \| shares	1,100,607
Granted, Units \| shares	363,900
Vested, Units \| shares	(327,536)
Forfeited, Units \| shares	(58,632)
Non-vested Units, Ending Balance \| shares	1,078,339
CECONY
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested Units, Beginning Balance \| shares	880,523
Granted, Units \| shares	288,669
Vested, Units \| shares	(266,683)
Forfeited, Units \| shares	(49,252)
Non-vested Units, Ending Balance \| shares	853,257
TSR Portion
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Non-vested, Beginning Balance (dollars per share)	$ 42.33
Weighted Average Grant Date Fair Value, Granted (dollars per share)	57.67
Weighted Average Grant Date Fair Value, Vested (dollars per share)	49.45
Weighted Average Grant Date Fair Value, Forfeited (dollars per share)	43.84
Weighted Average Grant Date Fair Value Non-vested, Ending Balance (dollars per share)	$ 45.26
Adjustment percentage used for Performance awards	50.00%
TSR Portion \| CECONY
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Non-vested, Beginning Balance (dollars per share)	$ 42.58
Weighted Average Grant Date Fair Value, Granted (dollars per share)	57.22
Weighted Average Grant Date Fair Value, Vested (dollars per share)	49.34
Weighted Average Grant Date Fair Value, Forfeited (dollars per share)	43.54
Weighted Average Grant Date Fair Value Non-vested, Ending Balance (dollars per share)	$ 45.37
Adjustment percentage used for Performance awards	50.00%
Non-TSR Portion
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Non-vested, Beginning Balance (dollars per share)	$ 56.61
Weighted Average Grant Date Fair Value, Granted (dollars per share)	63.22
Weighted Average Grant Date Fair Value, Vested (dollars per share)	58.84
Weighted Average Grant Date Fair Value, Forfeited (dollars per share)	58.25
Weighted Average Grant Date Fair Value Non-vested, Ending Balance (dollars per share)	$ 58.08
Adjustment percentage used for Performance awards	50.00%
Non-TSR Portion \| CECONY
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Non-vested, Beginning Balance (dollars per share)	$ 56.70
Weighted Average Grant Date Fair Value, Granted (dollars per share)	63.12
Weighted Average Grant Date Fair Value, Vested (dollars per share)	58.83
Weighted Average Grant Date Fair Value, Forfeited (dollars per share)	58.14
Weighted Average Grant Date Fair Value Non-vested, Ending Balance (dollars per share)	$ 58.12

Share Based Compensation Arrangement Percentage of RSU

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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