Capitalization - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Schedule of Capitalization [Line Items]
Common stock shares, outstanding | shares	21,976,200	21,976,200
Percentage limitation for income available for dividends (not more than)	100.00%
Rolling average calculation of income available for dividends (years)	2 years
Tax-exempt debt issued, value	$ 450,000,000
Long-term debt, fair value	13,856,000,000	$ 13,913,000,000
Tax-exempt debt	1,086,000,000	1,130,000,000
Long-term debt	12,745,000,000	12,106,000,000
Deferred finance costs	$ 91,000,000	85,000,000
Debt instrument, covenant description	Con Edison's ratio of consolidated debt to consolidated capital to exceed 0.675 to 1
Covenant principal balance amount limit	$ 100,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	13,220,000,000
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	$ 636,000,000
Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated capital for tax exempt financing	0.675
Transition Bonds, Issued in 2004
Schedule of Capitalization [Line Items]
Long-term debt	$ 15,000,000	18,000,000
CECONY
Schedule of Capitalization [Line Items]
Long-term debt, fair value	12,427,000,000	12,770,000,000
Tax-exempt debt	1,086,000,000	1,086,000,000
Long-term debt	11,437,000,000	11,138,000,000
Deferred finance costs	78,000,000	76,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	11,791,000,000
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
Tax-exempt debt	636,000,000
CECONY | Minimum
Schedule of Capitalization [Line Items]
Covenant principal balance amount limit	150,000,000
CECONY | Maximum
Schedule of Capitalization [Line Items]
Covenant principal balance amount limit	$ 100,000,000
Ratio of consolidated debt to consolidated capital for tax exempt financing	0.65
New Accounting Pronouncement, Early Adoption, Effect | Other Assets
Schedule of Capitalization [Line Items]
Deferred finance costs	$ (91,000,000)	(85,000,000)
New Accounting Pronouncement, Early Adoption, Effect | Other Assets | CECONY
Schedule of Capitalization [Line Items]
Deferred finance costs	(78,000,000)	(76,000,000)
New Accounting Pronouncement, Early Adoption, Effect | Long-term Debt
Schedule of Capitalization [Line Items]
Deferred finance costs	91,000,000	85,000,000
New Accounting Pronouncement, Early Adoption, Effect | Long-term Debt | CECONY
Schedule of Capitalization [Line Items]
Deferred finance costs	$ 78,000,000	$ 76,000,000