Schedule II - Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Detail) (Allowance For Uncollectible Accounts [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Balance at Beginning of Period	$ 105	$ 97	$ 84
Charged To Costs And Expenses	86	96	99
Charged To Other Accounts
Deductions	88	88	86
Balance At End of Period	103	105	97
CECONY [Member]
Balance at Beginning of Period	96	88	75
Charged To Costs And Expenses	82	90	91
Charged To Other Accounts
Deductions	83	82	78
Balance At End of Period	$ 95	$ 96	$ 88