Schedule II - Valuation and Qualifying Accounts (Details) - Allowance For Uncollectible Accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 74	$ 68	$ 70
Charged To Costs And Expenses	72	77	62
Charged To Other Accounts	0	0	0
Deductions	8	(71)	(64)
Balance At End of Period	154	74	68
CECONY
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	68	61	65
Charged To Costs And Expenses	65	72	56
Charged To Other Accounts	0	0	0
Deductions	10	(65)	(60)
Balance At End of Period	$ 143	$ 68	$ 61