Capitalization - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended
	Jun. 30, 2020	Jan. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jul. 31, 2020	Dec. 31, 2019
Schedule of Capitalization [Line Items]
Number of shares of common stock issued		1,050,000
Value of common stock issued		$ 88,000,000	$ 0	$ 0	$ 88,000,000	$ 0	$ 400,000,000	$ 425,000,000
Face amount of debt									$ 820,000,000
PG&E Project
Schedule of Capitalization [Line Items]
Short-term debt										$ 1,001,000,000
Long-term debt			898,000,000
Debentures | 3.35% Debentures Due 2030 | CECONY
Schedule of Capitalization [Line Items]
Face amount of debt					$ 600,000,000
Interest rate					3.35%
Debentures | 3.95% Debentures Due 2050 | CECONY
Schedule of Capitalization [Line Items]
Face amount of debt					$ 1,000,000,000
Interest rate					3.95%
Debentures | 4.45% 10 Year Debentures | CECONY
Schedule of Capitalization [Line Items]
Face amount of debt	$ 350,000,000			$ 350,000,000
Interest rate	4.45%			4.45%
Debt instrument term	10 years
Debentures | 2.02% Debentures Due 2030 | CECONY
Schedule of Capitalization [Line Items]
Face amount of debt			$ 35,000,000
Interest rate			2.02%
Debentures | 3.24% Debentures Due 2050 | CECONY
Schedule of Capitalization [Line Items]
Face amount of debt			$ 40,000,000
Interest rate			3.24%