Summary of Significant Accounting Policies and Other Matters - Adoption of New Standard (Details)	3 Months Ended
	Mar. 31, 2020 USD ($)
Accounting Policies [Abstract]
Increase in allowance for uncollectible accounts resulting from COVID-19 pandemic	$ 5,000,000
Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	70
Recoveries	2
Write-offs	(18)
Reserve adjustments	21
Ending Balance	75
Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	4
Recoveries	0
Write-offs	0
Reserve adjustments	1
Ending Balance	5
CECONY | Accounts receivable - customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	65
Recoveries	2
Write-offs	(18)
Reserve adjustments	21
Ending Balance	70
CECONY | Other receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3
Recoveries	0
Write-offs	0
Reserve adjustments	0
Ending Balance	$ 3