Current Expected Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 33
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	148	$ 70
Recoveries	3	2
Write-offs	(21)	(18)
Reserve adjustments	51	21
Ending Balance March 31,	181	75
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	7	4
Recoveries	0	0
Write-offs	(1)	0
Reserve adjustments	1	1
Ending Balance March 31,	7	5
CECONY
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic		5
CECONY | Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	138	65
Recoveries	3	2
Write-offs	(20)	(18)
Reserve adjustments	50	21
Ending Balance March 31,	171	70
CECONY | Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	4	3
Recoveries	0	0
Write-offs	0	0
Reserve adjustments	1	0
Ending Balance March 31,	$ 5	$ 3