Pension Benefits - Additional Information (Details) - Pension Benefits $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions	$ 472
Contributions	469
CECONY
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions	433
Contributions	431
CECONY \| Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions	$ 17

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration