Derivative Instruments And Hedging Activities (Aggregate Fair Value Of All Derivative Instruments With Credit Risk Related Contingent Features) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Aggregate fair value - net liabilities	$ 209	[1]
Collateral posted	60	[1]
Additional Collateral Required Due To Loss Of Unsecured Credit [Member]
Derivatives, Fair Value [Line Items]
Collateral posted	51
Additional collateral	20	[1],[2],[3]
Additional Collateral Aggregate Fair Value Down Below Investment Grade [Member]
Derivatives, Fair Value [Line Items]
Collateral posted	19
Additional collateral	$ 195	[1],[2],[3],[4]

[1] Non-derivative transactions for the purchase and sale of electricity and gas and qualifying derivative instruments, which have been designated as normal purchases or normal sales, are excluded from the table. These transactions primarily include purchases of electricity from independent system operators. In the event the Utilities and Con Edison's competitive energy businesses were no longer extended unsecured credit for such purchases, the Companies would be required to post collateral, which at December 31, 2011, would have amounted to an estimated $51 million for Con Edison, including $11 million for CECONY. For certain other such non-derivative transactions, the Companies could be required to post collateral under certain circumstances, including in the event counterparties had reasonable grounds for insecurity.

[2] The Companies measure the collateral requirements by taking into consideration the fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liabilities position plus amounts owed to counterparties for settled transactions and amounts required by counterparties for minimum financial security. The fair value amounts represent unrealized losses, net of any unrealized gains where the Companies have a legally enforceable right of setoff.

[3] The current ratings are Moody's, S&P and Fitch long-term credit rating of, as applicable, Con Edison (Baa1/BBB+/BBB+), CECONY (A3/A-/A-) or O&R (Baa1/A-/A-). Credit ratings assigned by rating agencies are expressions of opinions that are subject to revision or withdrawal at any time by the assigning rating agency.

[4] Derivative instruments that are net assets have been excluded from the table. At December 31, 2011, if Con Edison had been downgraded to below investment grade, it would have been required to post additional collateral for such derivative instruments of not more than $19 million.