Capitalization (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010
Schedule of Capitalization [Line Items]
Common stock, shares, outstanding	21,976,200	21,976,200
Percentage limitation for income available for dividends	100.00%
Rolling average calculation of income available for dividends, years	2
Tax exempt debt issued, value	$ 269
Long-term debt	10,673	10,676
Debt instrument, covenant description	Con Edison's ratio of consolidated debt to consolidated capital to exceed 0.675 to 1.
Covenant principal balance amount limit	100
Transition Bonds, Issued 2004 [Member]
Schedule of Capitalization [Line Items]
Long-term debt	$ 29	$ 32