Capitalization - Carrying Amounts and Fair Values of Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Unamortized debt expense	$ 220	$ 215
Carrying Amount
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	22,110	22,349
Fair Value
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	25,551	26,808
CECONY \| Subsidiaries
Debt Instrument [Line Items]
Unamortized debt discount	189	176
CECONY \| Carrying Amount \| Subsidiaries
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	17,635	16,789
CECONY \| Fair Value \| Subsidiaries
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	$ 20,854	$ 20,974

Amount, after accumulated amortization, of debt discount.

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=124435984&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

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant