Capitalization - Additional Information (Details) - USD ($)	1 Months Ended					3 Months Ended
	Jun. 30, 2019	May 31, 2019	Apr. 30, 2019	Mar. 31, 2019	Feb. 28, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Nov. 30, 2019	Oct. 31, 2019	Sep. 30, 2019
Schedule of Capitalization [Line Items]
Number of shares of common stock issued (shares)				5,649,369
Value of common stock issued				$ 425,000,000		$ 400,000,000	$ 425,000,000	$ 705,000,000
Term loan								825,000,000				$ 0
PG&E Project
Schedule of Capitalization [Line Items]
Term loan												$ 1,012,000,000
Clean Energy Businesses
Schedule of Capitalization [Line Items]
Non-recourse debt								2,076,000,000
Clean Energy Businesses | Long-term debt due within one year
Schedule of Capitalization [Line Items]
Non-recourse debt								1,965,000,000
Clean Energy Businesses | Long-term debt
Schedule of Capitalization [Line Items]
Non-recourse debt								$ 111,000,000
Term Loan
Schedule of Capitalization [Line Items]
Face amount of debt					$ 825,000,000
Debt term					2 years
Repayment of debt	$ 150,000,000
Debentures | 4.125% Debentures Due 2049 | CECONY
Schedule of Capitalization [Line Items]
Face amount of debt		$ 700,000,000
Interest rate		4.125%
Debentures | 6.65% 10-Year Debentures | CECONY
Schedule of Capitalization [Line Items]
Debt term			10 years
Repayment of debt			$ 475,000,000
Interest rate			665.00%
Transition Bond | O&R
Schedule of Capitalization [Line Items]
Repayment of debt		$ 1,000,000
Secured Debt | Term Loan Due 2026 | Con Edison Development
Schedule of Capitalization [Line Items]
Borrowings		$ 464,000,000
Common Stock
Schedule of Capitalization [Line Items]
Number of shares of common stock issued (shares)						5,000,000	6,000,000	10,000,000
Value of common stock issued						$ 1,000,000
Forward Contracts
Schedule of Capitalization [Line Items]
Common stock reserved for issuance (shares)		5,800,000										1,050,000
Share price (dollars per share)		$ 84.83
Forward Contracts | Common Stock
Schedule of Capitalization [Line Items]
Number of shares of common stock issued (shares)	4,750,000
Value of common stock issued	$ 400,000,000
Scenario, Forecast | Debentures | 3.73% Debentures Due 2049 | O&R
Schedule of Capitalization [Line Items]
Face amount of debt										$ 43,000,000
Interest rate										3.73%
Scenario, Forecast | Debentures | 2.94% Debentures Due 2029 | O&R
Schedule of Capitalization [Line Items]
Face amount of debt									$ 44,000,000
Interest rate									2.94%
Scenario, Forecast | Debentures | 3.46% Debentures Due 2039 | O&R
Schedule of Capitalization [Line Items]
Face amount of debt									$ 38,000,000
Interest rate									3.46%
Subsequent Event | Senior Notes | 3.82% Senior Notes Due 2038 | Con Edison Development
Schedule of Capitalization [Line Items]
Face amount of debt											$ 303,000,000
Interest rate											3.82%