Schedule I - Condensed Financial Information - Condensed Statement of Income and Comprehensive Income (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Condensed Consolidating Statement Of Operation [Line Items]
Interest expense	$ (591)	$ (719)	$ (604)
NET INCOME FOR COMMON STOCK	1,092	1,062	1,138
Comprehensive Income for Common Stock	1,072	1,090	1,143
Net Income Per Common Share - Basic	$ 3.73	$ 3.62	$ 3.88
Net Income Per Common Share - Diluted	$ 3.71	$ 3.61	$ 3.86
DIVIDENDS DECLARED PER SHARE OF COMMON STOCK	$ 2.52	$ 2.46	$ 2.42
Average Number Of Shares Outstanding-Basic	292.9	292.9	292.9
Average Number Of Shares Outstanding-Diluted	294.0	294.4	294.5
Consolidated Edison Inc [Member]
Schedule Of Condensed Consolidating Statement Of Operation [Line Items]
Equity in earnings of subsidiaries	1,101	1,062	1,154
Other income (deductions), net of taxes	19	29	12
Interest expense	(28)	(29)	(28)
NET INCOME FOR COMMON STOCK	1,092	1,062	1,138
Comprehensive Income for Common Stock	$ 1,072	$ 1,090	$ 1,143
Net Income Per Common Share - Basic	$ 3.73	$ 3.62	$ 3.88
Net Income Per Common Share - Diluted	$ 3.71	$ 3.61	$ 3.86
DIVIDENDS DECLARED PER SHARE OF COMMON STOCK	$ 2.52	$ 2.46	$ 2.42
Average Number Of Shares Outstanding-Basic	292.9	292.9	292.9
Average Number Of Shares Outstanding-Diluted	294.0	294.4	294.5