Other Postretirement Benefits - Schedule of Change of Assumed Health Care Cost Trend Rate (Details) - Other Postretirement Benefits $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Increase
Effect on accumulated other postretirement benefit obligation	$ 13
Effect on service cost and interest cost components for 2017	2
Decrease
Effect on accumulated other postretirement benefit obligation	11
Effect on service cost and interest cost components for 2017	0
CECONY
Increase
Effect on accumulated other postretirement benefit obligation	(20)
Effect on service cost and interest cost components for 2017	(1)
Decrease
Effect on accumulated other postretirement benefit obligation	35
Effect on service cost and interest cost components for 2017	$ 1

Defined Benefit Plan, Effect of One Percentage Point Decrease [Abstract]

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- Definition

Defined Benefit Plan, Effect of One Percentage Point Increase [Abstract]

+ References

No definition available.

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- Definition

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.

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Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

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Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate.

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