Capitalization - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)
Schedule of Capitalization [Line Items]
Percentage limitation for income available for dividends (not more than)	100.00%
Rolling average calculation of income available for dividends (years)	2 years
Long-term debt	$ 16,029,000,000	$ 14,774,000,000
Non-recourse debt	$ 915,000,000	845,000,000
Ratio of consolidated debt to consolidated total capital	0.51
Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated total capital	0.65
Transition Bonds, Issued in 2004
Schedule of Capitalization [Line Items]
Long-term debt	$ 7,000,000	11,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	17,511,000,000
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
Notes
Schedule of Capitalization [Line Items]
Covenant principal balance amount limit	$ 100,000,000
Notes | Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated total capital	0.675
CECONY
Schedule of Capitalization [Line Items]
Common stock shares, outstanding | shares	21,976,200
Long-term debt	$ 13,265,000,000	12,073,000,000
Ratio of consolidated debt to consolidated total capital	0.52
CECONY | Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated total capital	0.65
Covenant principal balance amount limit	$ 100,000,000
CECONY | Minimum
Schedule of Capitalization [Line Items]
Covenant principal balance amount limit	150,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	14,527,000,000
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
CECONY | Tax-Exempt Debt
Schedule of Capitalization [Line Items]
Tax-exempt debt issued, value	450,000,000
Long-term debt	1,086,000,000	$ 1,086,000,000
CECONY | Tax-Exempt Debt | Level 3
Schedule of Capitalization [Line Items]
Long-term debt	$ 636,000,000