Current Expected Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 94	$ 12	$ 127	$ 18
Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	91	11	124	16
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at April 1,	181	75	148	70
Recoveries	3	2	6	4
Write-offs	(21)	(15)	(41)	(34)
Reserve adjustments	112	25	162	47
Ending Balance June 30,	275	87	275	87
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at April 1,	7	5	7	4
Recoveries	0	0	0	0
Write-offs	0	(1)	(1)	(1)
Reserve adjustments	0	1	1	2
Ending Balance June 30,	7	5	7	5
CECONY | Accounts receivable - customers | Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at April 1,	171	70	138	65
Recoveries	2	2	5	4
Write-offs	(19)	(14)	(39)	(32)
Reserve adjustments	108	23	158	44
Ending Balance June 30,	262	81	262	81
CECONY | Other receivables | Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at April 1,	5	3	4	3
Recoveries	0	0	0	0
Write-offs	0	0	0	(1)
Reserve adjustments	(1)	0	0	1
Ending Balance June 30,	$ 4	$ 3	$ 4	$ 3