Income Tax (Schedule Of Differences On Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Depreciation	$ 3,699	$ 3,083
Regulatory asset - future income tax	1,971	1,760
Unrecognized pension and other postretirement costs	2,554	1,775
State income tax	892	759
Capitalized overheads	536	508
Pension	682	625
Investment tax credits	55	61
Other	696	720
Total deferred tax liabilities	11,085	9,291
Unrecognized pension and other postretirement costs	2,554	1,775
Regulatory liability - future income tax	173	168
Other	1,061	741
Total deferred tax assets	3,788	2,684
Net deferred tax liabilities and investment tax credits	7,297	6,607
Deferred tax liabilities and investment tax credits - Non current	7,563	6,769
Deferred tax assets - Current	(266)	(162)
Total deferred tax liabilities and investment tax credits	7,297	6,607
CECONY [Member]
Deferred tax assets - Current	$ (157)	$ (131)