Pension Benefits - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension liability	$ 361,000,000
Investments value	330,000,000	$ 273,000,000
CECONY
Defined Benefit Plan Disclosure [Line Items]
Pension liability	340,000,000
Investments value	301,000,000	246,000,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets and liabilities for future income taxes, net	368,000,000
Charge to OCI	4,000,000
Net loss estimated to be amortized	689,000,000
Prior service cost estimated to be amortized	(17,000,000)
Investments value	14,274,000,000	12,472,000,000	$ 11,759,000,000	$ 11,495,000,000
Accumulated benefit obligation	13,897,000,000	12,655,000,000	12,909,000,000
Defined benefit plan, bond amount (excess of)	50,000,000
Estimated future employer contributions	473,000,000
Pension Benefits | CECONY
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets and liabilities for future income taxes, net	353,000,000
Charge to OCI	1,000,000
Net loss estimated to be amortized	654,000,000
Prior service cost estimated to be amortized	(19,000,000)
Investments value	13,519,000,000	11,815,000,000	11,141,000,000	$ 10,897,000,000
Accumulated benefit obligation	12,972,000,000	11,806,000,000	$ 12,055,000,000
Estimated future employer contributions	435,000,000
Other Nonqualified Supplemental Defined Benefit Pension
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	331,000,000	303,000,000
Other Nonqualified Supplemental Defined Benefit Pension | CECONY
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 297,000,000	$ 268,000,000