Capitalization - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2015 USD ($) project	Dec. 31, 2014 USD ($)
Schedule of Capitalization [Line Items]
Number of solar projects securing notes | project	4
Long-term debt, fair value	$ 13,498,000,000	$ 13,998,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	12,862,000,000
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
CECONY
Schedule of Capitalization [Line Items]
Long-term debt, fair value	12,206,000,000	$ 12,846,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	11,570,000,000
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
Tax-exempt debt	636,000,000
Secured Debt | 4.95% debentures due 2045 | O&R
Schedule of Capitalization [Line Items]
Debt Instrument, face amount	$ 120,000,000
Debt instrument, interest rate (percent)	4.95%
Senior Notes | 3.94% Senior Notes due 2036 | Con Edison Development
Schedule of Capitalization [Line Items]
Debt Instrument, face amount	$ 118,000,000
Debt instrument, interest rate (percent)	3.94%