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Short-Term Borrowing (Details) - USD ($)	1 Months Ended		6 Months Ended
Short-Term Borrowing (Details) - USD ($)	Jul. 31, 2021	May 31, 2021	Jun. 30, 2021	Apr. 30, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Commercial paper, outstanding			$ 1,052,000,000		$ 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]
Outstanding borrowings			403,000,000		165,000,000
Banks' commitments under construction loan facility			$ 442,000,000		$ 613,000,000
April 2021 Credit Agreement, Variable Rate 364 Day Term Loan \| Line of Credit
Short-term Debt [Line Items]
Maximum borrowing capacity				$ 500,000,000
Debt instrument term			364 days
Proceeds from lines of credit		$ 500,000,000
April 2021 Credit Agreement, Variable Rate 364 Day Term Loan \| Line of Credit \| Subsequent Event
Short-term Debt [Line Items]
Repayments of 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			0.20%		0.30%
CECONY \| Subsidiaries
Short-term Debt [Line Items]
Commercial paper, outstanding			$ 1,000,000,000		$ 1,660,000,000
CECONY \| Commercial Paper \| Subsidiaries
Short-term Debt [Line Items]
Weighted average interest rate			0.20%		0.30%