Schedule II - Valuation and Qualifying Accounts (Details) - Allowance For Uncollectible Accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 96	$ 106	$ 103
Charged To Costs And Expenses	63	77	98
Charged To Other Accounts	0	0	0
Deductions	76	87	95
Balance At End of Period	83	96	106
CECONY
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	91	98	95
Charged To Costs And Expenses	57	69	91
Charged To Other Accounts	0	0	0
Deductions	70	76	88
Balance At End of Period	$ 78	$ 91	$ 98