Consolidated Statement Of Common Shareholders' Equity (USD $) In Millions, except Share data	Common Stock [Member] CECONY [Member]	Common Stock [Member]	Additional Paid-In Capital [Member] CECONY [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member] CECONY [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Repurchased Con Edison Stock [Member] CECONY [Member]	Capital Stock Expense [Member] CECONY [Member]	Capital Stock Expense [Member]	Accumulated Other Comprehensive Income/(Loss) [Member] CECONY [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	CECONY [Member]	Total
BEGINNING BALANCE at Dec. 31, 2008	$ 589	$ 29	$ 3,664	$ 4,112	$ 5,780	$ 6,685	$ (1,001)	$ (962)	$ (60)	$ (60)	$ (20)	$ (67)	$ 8,991	$ 9,698
BEGINNING BALANCE (in shares) at Dec. 31, 2008	235,488,094	273,721,686					23,210,700
Net income					792								792	879
Capital contribution by parent			213						(2)				211
Net income for common stock						868							781	868
Common stock dividends					(652)	(649)							(652)	(649)
Cumulative preferred dividends					(11)								(11)	(11)
Issuance of common shares - public offering		1		214						(2)				213
Issuance of common shares - public offering (in shares)		5,000,000
Issuance of common shares - dividend reinvestment and employee stock plans				94										94
Issuance of common shares - dividend reinvestment and employee stock plans (in shares)		2,402,055
Other comprehensive income											16	25	16	25
ENDING BALANCE at Dec. 31, 2009	589	30	3,877	4,420	5,909	6,904	(1,001)	(962)	(62)	(62)	(4)	(42)	9,347	10,249
ENDING BALANCE (in shares) at Dec. 31, 2009	235,488,094	281,123,741					23,210,700
Net income					904								904	1,003
Capital contribution by parent			357						(2)				355
Net income for common stock						992							893	992
Common stock dividends					(670)	(676)							(670)	(676)
Cumulative preferred dividends					(11)								(11)	(11)
Issuance of common shares - public offering		1		307						(2)				306
Issuance of common shares - public offering (in shares)		6,300,000
Issuance of common shares - dividend reinvestment and employee stock plans				188										188
Issuance of common shares - dividend reinvestment and employee stock plans (in shares)		4,192,593
Other comprehensive income											(2)	2	(2)	2
ENDING BALANCE at Dec. 31, 2010	589	31	4,234	4,915	6,132	7,220	(1,001)	(962)	(64)	(64)	(6)	(40)	9,923	11,061
ENDING BALANCE (in shares) at Dec. 31, 2010	235,488,094	291,616,334					23,210,700						235,488,094	291,616,334
Net income					989								989	1,062
Net income for common stock						1,051							978	1,051
Common stock dividends					(681)	(703)							(681)	(703)
Cumulative preferred dividends					(11)								(11)	(11)
Issuance of common shares - dividend reinvestment and employee stock plans		1		76			55							132
Issuance of common shares - dividend reinvestment and employee stock plans (in shares)		1,272,187					(1,538,166)
Common stock repurchases							(87)							(87)
Common stock repurchases (in shares)							1,521,541
Other comprehensive income											(2)	(18)	(2)	(18)
ENDING BALANCE at Dec. 31, 2011	$ 589	$ 32	$ 4,234	$ 4,991	$ 6,429	$ 7,568	$ (1,033)	$ (962)	$ (64)	$ (64)	$ (8)	$ (58)	$ 10,218	$ 11,436
ENDING BALANCE (in shares) at Dec. 31, 2011	235,488,094	292,888,521					23,194,075						235,488,094	292,888,521