Current Expected Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 38	$ 31	$ 165	$ 48
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Reserve adjustments			165	48
Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Reserve adjustments			162	45
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at July 1,	275	87	148	70
Recoveries	3	2	9	6
Write-offs	(24)	(4)	(66)	(37)
Reserve adjustments	59	33	222	79
Ending Balance September 30,	313	118	313	118
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at July 1,	7	5	7	4
Recoveries	0	0	0	0
Write-offs	0	0	(1)	(1)
Reserve adjustments	0	1	1	3
Ending Balance September 30,	7	6	7	6
CECONY | Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	38	30	162	46
CECONY | Accounts receivable - customers | Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at July 1,	262	81	138	65
Recoveries	3	2	8	6
Write-offs	(23)	(3)	(62)	(35)
Reserve adjustments	58	31	216	75
Ending Balance September 30,	300	111	300	111
CECONY | Other receivables | Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at July 1,	4	3	4	3
Recoveries	0	0	0	0
Write-offs	0	0	0	0
Reserve adjustments	1	1	1	1
Ending Balance September 30,	$ 5	$ 4	$ 5	$ 4