Summary of Significant Accounting Policies and Other Matters - Adoption of New Standard (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 12	$ 18
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	75	70
Recoveries	2	4
Write-offs	(15)	(34)
Reserve adjustments	25	47
Ending Balance	87	87
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	5	4
Recoveries	0	0
Write-offs	(1)	(1)
Reserve adjustments	1	2
Ending Balance	5	5
CECONY
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	11	16
CECONY | Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	70	65
Recoveries	2	4
Write-offs	(14)	(32)
Reserve adjustments	23	44
Ending Balance	81	81
CECONY | Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3	3
Recoveries	0	0
Write-offs	0	(1)
Reserve adjustments	0	1
Ending Balance	$ 3	$ 3