Summary of Significant Accounting Policies and Other Matters - Adoption of New Standard (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 78
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	70
Recoveries	8
Write-offs	(54)
Reserve adjustments	124
Ending Balance	148
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	4
Recoveries	0
Write-offs	(2)
Reserve adjustments	5
Ending Balance	7
CECONY
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	73
CECONY | Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	65
Recoveries	6
Write-offs	(50)
Reserve adjustments	117
Ending Balance	138
CECONY | Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3
Recoveries	0
Write-offs	(1)
Reserve adjustments	2
Ending Balance	$ 4