Statement of Shareholders' Equity (USD $) In Millions	Total	CECONY	Common Stock [Member]	Common Stock [Member] CECONY	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] CECONY	Retained Earnings [Member]	Retained Earnings [Member] CECONY	Treasury Stock [Member]	Capital Stock Expense [Member]	Capital Stock Expense [Member] CECONY	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] CECONY	Repurchased Con Edison Stock [Member] CECONY
BALANCE at Dec. 31, 2010	$ 11,061	$ 9,923	$ 31	$ 589	$ 4,915	$ 4,234	$ 7,220	$ 6,132	$ (1,001)	$ (64)	$ (64)	$ (40)	$ (6)	$ (962)
BALANCE (In Shares) at Dec. 31, 2010			291,616,334	235,488,094					23,210,700
Net income for common stock	311						311
Net Income		271						271
Common stock dividend to parent	(175)	(170)					(175)	(170)
Issuance of common shares - dividend reinvestment and employee stock plans (In Shares)			656,049
Cumulative preferred dividends		(3)						(3)
Issuance of common shares - dividend reinvestment and employee stock plans	31		1		30
Other comprehensive income	3											3
BALANCE at Mar. 31, 2011	11,231	10,021	32	589	4,945	4,234	7,356	6,230		(64)	(64)	(37)	(6)	(962)
BALANCE (In Shares) at Mar. 31, 2011			292,272,383	235,488,094
BALANCE at Dec. 31, 2010	11,061	9,923		589		4,234			(1,001)	(64)	(64)		(6)	(962)
BALANCE (In Shares) at Dec. 31, 2010				235,488,094					23,210,700
Net income for common stock	477	426
Net Income	483	432
Cumulative preferred dividends	6
BALANCE at Jun. 30, 2011	11,251	10,008		589		4,234				(64)	(64)		(6)	(962)
BALANCE (In Shares) at Jun. 30, 2011				235,488,094
BALANCE at Mar. 31, 2011	11,231	10,021	32	589	4,945	4,234	7,356	6,230	(1,001)	(64)	(64)	(37)	(6)	(962)
BALANCE (In Shares) at Mar. 31, 2011			292,272,383	235,488,094					23,210,700
Net income for common stock	165	157					165
Net Income	168	160						160
Common stock dividend to parent	(175)	(170)					(175)	(170)
Issuance of common shares - dividend reinvestment and employee stock plans (In Shares)			603,513						(182,942)
Cumulative preferred dividends	3	(3)						(3)
Issuance of common shares - dividend reinvestment and employee stock plans	37				32				5
Common stock repurchases (In Shares)									178,942
Common stock repurchases	(9)								(9)
Other comprehensive income	2											2
BALANCE at Jun. 30, 2011	11,251	10,008	32	589	4,977	4,234	7,346	6,217	(1,005)	(64)	(64)	(35)	(6)	(962)
BALANCE (In Shares) at Jun. 30, 2011			292,875,896	235,488,094					23,206,700
BALANCE at Dec. 31, 2011	11,436	10,218	32	589	4,991	4,234	7,568	6,429	(1,033)	(64)	(64)	(58)	(8)	(962)
BALANCE (In Shares) at Dec. 31, 2011			292,888,521	235,488,094					23,194,075
Net income for common stock	277						277
Net Income		276						276
Common stock dividend to parent	(177)	(171)					(177)	(171)
Issuance of common shares - dividend reinvestment and employee stock plans (In Shares)			(7,225)						7,225
Cumulative preferred dividends		(3)						(3)
Issuance of common shares - dividend reinvestment and employee stock plans	(2)								(2)
Preferred stock redemption	4	4								4	4
Other comprehensive income	7											7
BALANCE at Mar. 31, 2012	11,545	10,324	32	589	4,991	4,234	7,668	6,531	(1,035)	(60)	(60)	(51)		(962)
BALANCE (In Shares) at Mar. 31, 2012			292,881,296	235,488,094					23,201,300
BALANCE at Dec. 31, 2011	11,436	10,218		589	4,991	4,234							(8)	(962)
BALANCE (In Shares) at Dec. 31, 2011				235,488,094
Net income for common stock	491	436
Net Income	494	439
Cumulative preferred dividends	3
BALANCE at Jun. 30, 2012	11,579	10,314		589	4,991	4,234					(60)			(962)
BALANCE (In Shares) at Jun. 30, 2012				235,488,094
BALANCE at Mar. 31, 2012	11,545	10,324	32	589	4,991	4,234	7,668	6,531	(1,035)	(60)		(51)	(8)	(962)
BALANCE (In Shares) at Mar. 31, 2012			292,881,296	235,488,094					23,201,300
Net income for common stock	214	163					214
Net Income	214	163						163
Common stock dividend to parent	(178)	(171)					(178)	(171)
Issuance of common shares - dividend reinvestment and employee stock plans	(1)		1,700						(1,700)	(1)
Other comprehensive income	(1)	(2)										(1)	(2)
BALANCE at Jun. 30, 2012	$ 11,579	$ 10,314	$ 32	$ 589	$ 4,991	$ 4,234	$ 7,704	$ 6,523	$ (1,035)	$ (61)	$ (60)	$ (52)	$ (10)	$ (962)
BALANCE (In Shares) at Jun. 30, 2012			292,882,996	235,488,094					23,199,600