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Short-Term Borrowing (Details) - USD ($)	1 Months Ended			9 Months Ended
Short-Term Borrowing (Details) - USD ($)	Aug. 31, 2021	Jul. 31, 2021	May 31, 2021	Sep. 30, 2021	Apr. 30, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Commercial paper, outstanding				$ 1,036,000,000		$ 1,705,000,000
Loans outstanding under the credit agreement				$ 0		0
Variable Rate Construction Loan Facility Maturing November 2021 \| Clean Energy Businesses \| Line of Credit
Short-term Debt [Line Items]
Repayments of lines of credit	$ 249,000,000
Line of credit terminated	$ 613,000,000
Banks' commitments under construction loan facility						613,000,000
Outstanding borrowings						$ 165,000,000
April 2021 Credit Agreement, Variable Rate 364 Day Term Loan \| Line of Credit
Short-term Debt [Line Items]
Repayments of lines of credit		$ 500,000,000
Maximum borrowing capacity					$ 500,000,000
Debt instrument term				364 days
Proceeds from lines of credit			$ 500,000,000
2.00% Debentures Due 2021
Short-term Debt [Line Items]
Debt instrument term			5 years
Interest rate			2.00%
Commercial Paper
Short-term Debt [Line Items]
Weighted average interest rate				0.10%		0.30%
CECONY \| Subsidiaries
Short-term Debt [Line Items]
Commercial paper, outstanding				$ 942,000,000		$ 1,660,000,000
CECONY \| Commercial Paper \| Subsidiaries
Short-term Debt [Line Items]
Weighted average interest rate				0.10%		0.30%