Capitalization - Carrying Amounts and Fair Values of Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Unamortized debt expense	$ 221	$ 215
Carrying Amount
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	22,280	22,349
Fair Value
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	25,655	26,808
CECONY \| Subsidiaries
Debt Instrument [Line Items]
Unamortized debt discount	188	176
CECONY \| Carrying Amount \| Subsidiaries
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	17,637	16,789
CECONY \| Fair Value \| Subsidiaries
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	$ 20,774	$ 20,974

Amount, after accumulated amortization, of debt discount.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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