Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		TOTAL ASSETS	TOTAL ASSETS
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		TOTAL CURRENT LIABILITIES	TOTAL CURRENT LIABILITIES
Derivative liabilities transferred from Level 3 to Level 2		$ 9,000,000	$ 0
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term of contract (in years)	3 years	3 years
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term of contract (in years)		3 years	3 years
CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities transferred from Level 3 to Level 2		$ 6,000,000	$ 0
Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		(5,000,000)
Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities transferred from Level 3 to Level 2			10,000,000
Commodity | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities transferred from Level 3 to Level 2			9,000,000
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		723,000,000	874,000,000
Derivative liabilities		314,000,000	90,000,000
Recurring | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		699,000,000	663,000,000
Recurring | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		(54,000,000)	(418,000,000)
Derivative liabilities		(65,000,000)	(182,000,000)
Recurring | Netting Adjustment | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		(52,000,000)	(388,000,000)
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		511,000,000	527,000,000
Derivative liabilities		22,000,000	26,000,000
Recurring | Level 1 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		494,000,000	505,000,000
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		264,000,000	732,000,000
Derivative liabilities		347,000,000	228,000,000
Recurring | Level 2 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		256,000,000	544,000,000
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		2,000,000	33,000,000
Derivative liabilities		10,000,000	18,000,000
Recurring | Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		1,000,000	2,000,000
Recurring | Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		100,000,000	142,000,000
Derivative liabilities		314,000,000	54,000,000
Recurring | Commodity | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		98,000,000	131,000,000
Derivative liabilities		287,000,000	44,000,000
Recurring | Commodity | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		(54,000,000)	(420,000,000)
Derivative liabilities		(65,000,000)	(184,000,000)
Recurring | Commodity | Netting Adjustment | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		(52,000,000)	(388,000,000)
Derivative liabilities		(65,000,000)	(180,000,000)
Recurring | Commodity | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		6,000,000	84,000,000
Derivative liabilities		22,000,000	18,000,000
Recurring | Commodity | Level 1 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		6,000,000	83,000,000
Derivative liabilities		20,000,000	18,000,000
Recurring | Commodity | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		146,000,000	476,000,000
Derivative liabilities		347,000,000	204,000,000
Recurring | Commodity | Level 2 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		143,000,000	434,000,000
Derivative liabilities		326,000,000	198,000,000
Recurring | Commodity | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		2,000,000	2,000,000
Derivative liabilities		10,000,000	16,000,000
Recurring | Commodity | Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		1,000,000	2,000,000
Derivative liabilities		6,000,000	8,000,000
Recurring | Commodity held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			73,000,000
Derivative liabilities			36,000,000
Recurring | Commodity held for sale | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			2,000,000
Derivative liabilities			2,000,000
Recurring | Commodity held for sale | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			6,000,000
Derivative liabilities			8,000,000
Recurring | Commodity held for sale | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			34,000,000
Derivative liabilities			24,000,000
Recurring | Commodity held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			31,000,000
Derivative liabilities			2,000,000
Recurring | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			106,000,000
Recurring | Interest Rate Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			106,000,000
Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		623,000,000	553,000,000
Recurring | Other | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		601,000,000	532,000,000
Recurring | Other | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Recurring | Other | Netting Adjustment | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Recurring | Other | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		505,000,000	437,000,000
Recurring | Other | Level 1 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		488,000,000	422,000,000
Recurring | Other | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		118,000,000	116,000,000
Recurring | Other | Level 2 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		113,000,000	110,000,000
Recurring | Other | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Recurring | Other | Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		$ 0	$ 0