Capitalization - Carrying Amounts and Fair Values of Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Unamortized debt expense	$ 204	$ 215
Carrying Amount
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	21,916	22,349
Fair Value
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	24,533	26,808
CECONY
Debt Instrument [Line Items]
Unamortized debt discount	173	176
CECONY \| Carrying Amount
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	16,791	16,789
CECONY \| Fair Value
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	$ 19,251	$ 20,974

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Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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