Capitalization - Additional Information (Details) - USD ($)	1 Months Ended		6 Months Ended
	May 31, 2018	Apr. 30, 2018	Jun. 30, 2018
Level 1
Schedule of Capitalization [Line Items]
Long-term debt, fair value			$ 636,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value			17,308,000,000
CECONY
Schedule of Capitalization [Line Items]
Tax-exempt debt			636,000,000
CECONY | Level 1
Schedule of Capitalization [Line Items]
Long-term debt, fair value			636,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value			14,472,000,000
CECONY | Debentures | 5.85% Debentures
Schedule of Capitalization [Line Items]
Face amount of debt		$ 600,000,000
Interest rate		5.85%
Debt term		10 years
CECONY | Debentures | 3.80% Debentures
Schedule of Capitalization [Line Items]
Face amount of debt	$ 300,000,000
Interest rate	3.80%
Debt term	10 years
CECONY | Debentures | 4.50% Debentures
Schedule of Capitalization [Line Items]
Face amount of debt	$ 700,000,000
Interest rate	4.50%
Debt term	40 years
CECONY | Debentures | Floating Rate Debentures
Schedule of Capitalization [Line Items]
Face amount of debt			$ 640,000,000