Capitalization - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2016	May 31, 2016	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2015	Feb. 29, 2016	Dec. 31, 2015
Schedule of Capitalization [Line Items]
Stock issued during the period, value			$ 702,000,000
Proceeds from long-term debt				$ 1,765,000,000	$ 238,000,000
Long-term debt, fair value	$ 16,681,000,000		16,681,000,000	16,681,000,000			$ 13,856,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	16,045,000,000		16,045,000,000	16,045,000,000
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000		636,000,000	636,000,000
CECONY
Schedule of Capitalization [Line Items]
Proceeds from long-term debt				550,000,000	$ 0
Long-term debt, fair value	13,917,000,000		13,917,000,000	13,917,000,000			$ 12,427,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	13,281,000,000		13,281,000,000	13,281,000,000
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000		636,000,000	636,000,000
Tax-exempt debt				636,000,000
Senior Notes | 4.21% Senior Notes due 2041 | Con Edison Development
Schedule of Capitalization [Line Items]
Debt Instrument, face amount						$ 218,000,000
Debt instrument, interest rate (percent)						4.21%
Senior Notes | 4.07% Senior Notes due 2036 | Con Edison Development
Schedule of Capitalization [Line Items]
Debt Instrument, face amount		$ 95,000,000
Debt instrument, interest rate (percent)		4.07%
Secured Debt | 2.00% Debentures due 2021
Schedule of Capitalization [Line Items]
Debt Instrument, face amount		$ 500,000,000
Debt instrument, interest rate (percent)		2.00%
Secured Debt | 3.85% Debentures due 2046 | CECONY
Schedule of Capitalization [Line Items]
Debt Instrument, face amount	$ 550,000,000		$ 550,000,000	$ 550,000,000
Debt instrument, interest rate (percent)	3.85%		3.85%	3.85%
Secured Debt | New Jersey Utility Agreement | Con Edison Solutions
Schedule of Capitalization [Line Items]
Debt instrument, interest rate (percent)	11.18%		11.18%	11.18%
Proceeds from long-term debt	$ 2,000,000
Unsecured Debt | Term Loan Credit Facility
Schedule of Capitalization [Line Items]
Debt Instrument, face amount	$ 400,000,000		$ 400,000,000	$ 400,000,000
Common Stock
Schedule of Capitalization [Line Items]
Stock issued during period (in shares)		10,000,000	10,000,000
Stock issued during the period, value		$ 702,000,000	$ 1,000,000
LIBOR | Senior Notes | 4.07% Senior Notes due 2036 | Con Edison Development
Schedule of Capitalization [Line Items]
Debt instrument, basis spread on variable rate (percent)	1.00%