Capitalization - Carrying Amounts and Fair Values of Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Carrying Amount	$ 10,974		$ 10,768
Fair Value	12,082		12,935
CECONY [Member]
Debt Instrument [Line Items]
Carrying Amount	9,841	[1]	9,845	[1]
Fair Value	$ 10,797		$ 11,751

[1] Rates are to be reset weekly or by auction held every 35 days; December 31, 2013 rates shown.