Capitalization - Additional Information (Detail) - USD ($)	1 Months Ended				3 Months Ended	9 Months Ended
	Oct. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	May 31, 2016	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2016	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		$ 16,325,000,000				16,325,000,000				$ 13,856,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value		15,689,000,000				15,689,000,000
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value		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		13,564,000,000				13,564,000,000				$ 12,427,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value		12,928,000,000				12,928,000,000
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value		$ 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
Debt instrument, interest rate (percent)			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%
Proceeds from long-term debt			$ 2,000,000
Secured Debt | 5.50% Debentures due 2016 | CECONY
Schedule of Capitalization [Line Items]
Debt instrument, interest rate (percent)		5.50%				5.50%
Redemption of debt		$ 400,000,000
Unsecured Debt | Term Loan Credit Facility
Schedule of Capitalization [Line Items]
Debt Instrument, face amount			$ 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%
Scenario, Forecast | Secured Debt | 3.88% Debentures due 2016 | O&R
Schedule of Capitalization [Line Items]
Debt Instrument, face amount								$ 75,000,000
Debt instrument, interest rate (percent)								3.88%
Subsequent Event | Secured Debt | 5.45% Debentures due 2016 | O&R
Schedule of Capitalization [Line Items]
Debt instrument, interest rate (percent)	5.45%
Redemption of debt	$ 75,000,000