Current Expected Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 20	$ 33	$ 19
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Reserve adjustments	19	33
Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Reserve adjustments	20	33
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	317	148	148
Recoveries	5	3
Write-offs	(30)	(21)
Reserve adjustments	44	51
Ending Balance March 31,	336	181	317
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	22	7	7
Recoveries	0	0
Write-offs	(3)	(1)
Reserve adjustments	6	1
Ending Balance March 31,	25	7	22
CECONY | Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	20		19
CECONY | Accounts receivable - customers | Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	304	138	138
Recoveries	4	3
Write-offs	(28)	(20)
Reserve adjustments	44	50
Ending Balance March 31,	324	171	304
CECONY | Other receivables | Subsidiaries
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance at January 1,	19	4	4
Recoveries	0	0
Write-offs	(2)	0
Reserve adjustments	6	1
Ending Balance March 31,	$ 23	$ 5	$ 19