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)	Non- controlling 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 (shares) at Dec. 31, 2019		333			23
Beginning Balance (shares) at Dec. 31, 2019										235
Beginning Balance at Dec. 31, 2019	$ 18,213	$ 35	$ 8,054	$ 11,100	$ (1,038)	$ (110)	$ (19)	$ 191
Beginning Balance at Dec. 31, 2019									$ 14,147	$ 589	$ 5,669	$ 8,919	$ (962)	$ (62)	$ (6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	392			375				17
Net income	375								406			406
Common stock dividends	(255)			(255)					(246)			(246)
Issuance of common shares – public offering (shares)		1
Issuance of common shares - public offering	88		88
Issuance of common shares for stock plans	26		26
Capital contribution by parent									25		25
Other comprehensive income	5						5		1						1
Distributions to noncontrolling interest	(2)							(2)
Ending Balance (shares) at Mar. 31, 2020		334			23
Ending Balance (shares) at Mar. 31, 2020										235
Ending Balance at Mar. 31, 2020	18,467	$ 35	8,168	11,220	$ (1,038)	(110)	(14)	206
Ending Balance at Mar. 31, 2020									14,333	$ 589	5,694	9,079	(962)	(62)	(5)
Beginning Balance (shares) at Dec. 31, 2020		342			23
Beginning Balance (shares) at Dec. 31, 2020										235
Beginning Balance at Dec. 31, 2020	19,065	$ 36	8,808	11,178	$ (1,038)	(112)	(25)	218
Beginning Balance at Dec. 31, 2020	18,847								14,849	$ 589	6,169	9,122	(962)	(62)	(7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	420			419				1
Net income	419								465			465
Common stock dividends	(265)			(265)					(247)			(247)
Issuance of common shares for stock plans	28		28
Capital contribution by parent									125		125
Other comprehensive income	4						4		0
Distributions to noncontrolling interest	(3)							(3)
Net proceeds from sale of equity interest	33							33
Ending Balance (shares) at Mar. 31, 2021		342			23
Ending Balance (shares) at Mar. 31, 2021										235
Ending Balance at Mar. 31, 2021	19,282	$ 36	$ 8,836	$ 11,332	$ (1,038)	$ (112)	$ (21)	$ 249
Ending Balance at Mar. 31, 2021	$ 19,033								$ 15,192	$ 589	$ 6,294	$ 9,340	$ (962)	$ (62)	$ (7)