Consolidated Statement of Equity/Shareholder's Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Capital Stock Expense	Accumulated Other Comprehensive Income/(Loss)	Noncontrolling Interest	CECONY	CECONY Common Stock	CECONY Additional Paid-In Capital	CECONY Retained Earnings	CECONY Repurchased Con Edison Stock	CECONY Capital Stock Expense	CECONY Accumulated Other Comprehensive Income/(Loss)
Beginning Balance (in shares) at Dec. 31, 2015		293			23					235
Beginning Balance at Dec. 31, 2015	$ 13,061	$ 32	$ 5,030	$ 9,123	$ (1,038)	$ (61)	$ (34)	$ 9							$ (9)
Beginning Balance at Dec. 31, 2015									$ 11,415	$ 589	$ 4,247	$ 7,611	$ (962)	$ (61)	(9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	310			310					310			310
Common stock dividends	(197)			(197)					(186)			(186)
Issuance of common shares for stock plans (in shares)		1
Issuance of common shares for stock plans	28		28
Capital contribution by parent									23		23
Other comprehensive income (loss)	0								0						0
Noncontrolling interest	(1)							(1)
Ending Balance (in shares) at Mar. 31, 2016		294			23					235
Ending Balance at Mar. 31, 2016									11,562	$ 589	4,270	7,735	(962)	(61)	(9)
Ending Balance at Mar. 31, 2016	13,201	$ 32	5,058	9,236	$ (1,038)	(61)	(34)	8
Beginning Balance (in shares) at Dec. 31, 2015		293			23					235
Beginning Balance at Dec. 31, 2015	13,061	$ 32	5,030	9,123	$ (1,038)	(61)	(34)	9							(9)
Beginning Balance at Dec. 31, 2015									11,415	$ 589	4,247	7,611	(962)	(61)	(9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,039								859
Other comprehensive income (loss)	2								1
Ending Balance (in shares) at Sep. 30, 2016		305			23					235
Ending Balance at Sep. 30, 2016									11,793	$ 589	4,323	7,912	(962)	(61)	(8)
Ending Balance at Sep. 30, 2016	14,275	$ 33	5,830	9,557	$ (1,038)	(83)	(32)	8							(8)
Beginning Balance (in shares) at Mar. 31, 2016		294			23					235
Beginning Balance at Mar. 31, 2016	13,201	$ 32	5,058	9,236	$ (1,038)	(61)	(34)	8
Beginning Balance at Mar. 31, 2016									11,562	$ 589	4,270	7,735	(962)	(61)	(9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	232			232					161			161
Common stock dividends	(204)			(204)					(186)			(186)
Issuance of common shares for stock plans	26		26
Issuance of common shares - public offering (in shares)		10
Issuance of common shares - public offering	702	$ 1	723			(22)
Capital contribution by parent									28		28
Other comprehensive income (loss)	1						1		1						1
Ending Balance (in shares) at Jun. 30, 2016		304			23					235
Ending Balance at Jun. 30, 2016									11,566	$ 589	4,298	7,710	(962)	(61)	(8)
Ending Balance at Jun. 30, 2016	13,958	$ 33	5,807	9,264	$ (1,038)	(83)	(33)	8							(8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	497			497					388			388
Common stock dividends	(204)			(204)					(186)			(186)
Issuance of common shares for stock plans (in shares)		1
Issuance of common shares for stock plans	23		23
Capital contribution by parent									25		25
Other comprehensive income (loss)	1						1		0						0
Ending Balance (in shares) at Sep. 30, 2016		305			23					235
Ending Balance at Sep. 30, 2016									11,793	$ 589	4,323	7,912	(962)	(61)	(8)
Ending Balance at Sep. 30, 2016	14,275	$ 33	5,830	9,557	$ (1,038)	(83)	(32)	8							(8)
Beginning Balance (in shares) at Dec. 31, 2016		305			23					235
Beginning Balance at Dec. 31, 2016	14,306	$ 33	5,854	9,559	$ (1,038)	(83)	(27)	8							(7)
Beginning Balance at Dec. 31, 2016	14,298								11,829	$ 589	4,347	7,923	(962)	(61)	(7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	388			388					339			339
Common stock dividends	(211)			(211)					(199)			(199)
Issuance of common shares for stock plans	24		24
Capital contribution by parent									22		22
Other comprehensive income (loss)	(1)						(1)		0						0
Ending Balance (in shares) at Mar. 31, 2017		305			23					235
Ending Balance at Mar. 31, 2017									11,991	$ 589	4,369	8,063	(962)	(61)	(7)
Ending Balance at Mar. 31, 2017	14,506	$ 33	5,878	9,736	$ (1,038)	(83)	(28)	8
Beginning Balance (in shares) at Dec. 31, 2016		305			23					235
Beginning Balance at Dec. 31, 2016	14,306	$ 33	5,854	9,559	$ (1,038)	(83)	(27)	8							(7)
Beginning Balance at Dec. 31, 2016	14,298								11,829	$ 589	4,347	7,923	(962)	(61)	(7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,020								883
Other comprehensive income (loss)	1								1
Ending Balance (in shares) at Sep. 30, 2017		310			23					235
Ending Balance at Sep. 30, 2017	15,102								12,395	$ 589	4,627	8,209	(962)	(62)	(6)
Ending Balance at Sep. 30, 2017	15,110	$ 33	6,274	9,944	$ (1,038)	(85)	(26)	8							(6)
Beginning Balance (in shares) at Mar. 31, 2017		305			23					235
Beginning Balance at Mar. 31, 2017	14,506	$ 33	5,878	9,736	$ (1,038)	(83)	(28)	8
Beginning Balance at Mar. 31, 2017									11,991	$ 589	4,369	8,063	(962)	(61)	(7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	175			175					143			143
Common stock dividends	(210)			(210)					(199)			(199)
Issuance of common shares for stock plans (in shares)		1
Issuance of common shares for stock plans	26		26
Capital contribution by parent									23		23
Other comprehensive income (loss)	1						1		0						0
Ending Balance (in shares) at Jun. 30, 2017		306			23					235
Ending Balance at Jun. 30, 2017									11,958	$ 589	4,392	8,007	(962)	(61)	(7)
Ending Balance at Jun. 30, 2017	14,498	$ 33	5,904	9,701	$ (1,038)	(83)	(27)	8							(7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	457			457					401			401
Common stock dividends	(214)			(214)					(199)			(199)
Issuance of common shares for stock plans	25		25
Issuance of common shares - public offering (in shares)		4
Issuance of common shares - public offering	343		345			(2)
Capital contribution by parent									234		235			(1)
Other comprehensive income (loss)	1						1		1						1
Ending Balance (in shares) at Sep. 30, 2017		310			23					235
Ending Balance at Sep. 30, 2017	15,102								$ 12,395	$ 589	$ 4,627	$ 8,209	$ (962)	$ (62)	(6)
Ending Balance at Sep. 30, 2017	$ 15,110	$ 33	$ 6,274	$ 9,944	$ (1,038)	$ (85)	$ (26)	$ 8							$ (6)