Derivative Instruments and Hedging Activities - Realized and Unrealized Gains (Losses) on Commodity Derivatives (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	$ 384	$ 16
Total deferred gains/(losses)	87	27
Net deferred gains/(losses) (a)	471	43
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	56	65
Gas purchased for resale
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	5	1
Non-utility revenue
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	(17)	3
Other operations and maintenance expense
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	3	2
Other interest expense
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	65	59
Deferred Derivative Gains, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	339	19
Deferred Derivative Gains, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	45	(3)
Deferred Derivative Losses, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(36)	4
Recoverable Energy Costs, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	157	0
Deferred Derivative Losses, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(34)	23
CECONY | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	353	14
Total deferred gains/(losses)	77	25
Net deferred gains/(losses) (a)	430	39
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	3	2
CECONY | Gas purchased for resale | Subsidiaries
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	0	0
CECONY | Non-utility revenue | Subsidiaries
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	0	0
CECONY | Other operations and maintenance expense | Subsidiaries
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	3	2
CECONY | Other interest expense | Subsidiaries
Pre-tax gains/(losses) recognized in income
Total pre-tax gains/(losses) recognized in income	0	0
CECONY | Deferred Derivative Gains, Current | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	312	17
CECONY | Deferred Derivative Gains, Noncurrent | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	41	(3)
CECONY | Deferred Derivative Losses, Current | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(32)	3
CECONY | Recoverable Energy Costs, Current | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	143	2
CECONY | Deferred Derivative Losses, Noncurrent | Subsidiaries
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	$ (34)	$ 20