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 at Dec. 31, 2016							$ (27)								$ (7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 388								$ 339
Other comprehensive income (loss)	(1)								0
Ending Balance at Mar. 31, 2017							(28)								(7)
Beginning Balance (in shares) at Dec. 31, 2017		310			23					235
Beginning Balance at Dec. 31, 2017	15,425	$ 34	$ 6,298	$ 10,235	$ (1,038)	$ (85)	(26)	$ 7							(6)
Beginning Balance at Dec. 31, 2017	15,418								12,439	$ 589	$ 4,649	$ 8,231	$ (962)	$ (62)	(6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	428			428					389			389
Common stock dividends	(221)			(221)					(211)			(211)
Issuance of common shares for stock plans (in shares)		1
Issuance of common shares for stock plans	25		25
Capital contribution by parent									45		45
Other comprehensive income (loss)	4						4		0
Ending Balance (in shares) at Mar. 31, 2018		311			23					235
Ending Balance at Mar. 31, 2018	15,654								$ 12,662	$ 589	$ 4,694	$ 8,409	$ (962)	$ (62)	(6)
Ending Balance at Mar. 31, 2018	$ 15,661	$ 34	$ 6,323	$ 10,442	$ (1,038)	$ (85)	$ (22)	$ 7							$ (6)