Leases - Lease Cost and Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 17	$ 17	$ 51	$ 50
Operating lease cash flows	7	6	15	15
CECONY \| Subsidiaries
Lessee, Lease, Description [Line Items]
Operating lease cost	17	17	51	49
Operating lease cash flows	$ 6	$ 6	$ 15	$ 14

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
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- Definition

Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
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-Name Accounting Standards Codification
-Section 55
-Paragraph 53
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
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-Name Accounting Standards Codification
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