Capitalization - Common Stock (Details) - USD ($) $ in Millions	1 Months Ended				12 Months Ended
	Jan. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 31, 2019	Nov. 30, 2018	Dec. 31, 2016
Schedule of Capitalization [Line Items]
Common stock, shares authorized (in shares)					500,000,000
Common stock, shares outstanding (in shares)				320,960,396	332,629,597	320,960,396
Treasury shares (in shares)					23,210,700
Shares issued (in shares)			5,649,369
Value of shares issued			$ 425		$ 825	$ 705	$ 343
Common Stock
Schedule of Capitalization [Line Items]
Common stock, shares outstanding (in shares)				321,000,000	333,000,000	321,000,000	310,000,000			305,000,000
Treasury shares (in shares)				23,210,700		23,210,700
Shares issued (in shares)				9,324,123	12,000,000	11,000,000	5,000,000
Value of shares issued				$ 705	$ 1		$ 1
Forward Contract
Schedule of Capitalization [Line Items]
Common stock, shares subject to forward sale agreements (in shares)					1,050,000			5,800,000	14,973,492
Forward Contract | Common Stock
Schedule of Capitalization [Line Items]
Shares issued (in shares)		4,750,000
Value of shares issued		$ 400
CECONY
Schedule of Capitalization [Line Items]
Common stock, shares authorized (in shares)					340,000,000
Common stock, shares outstanding (in shares)					235,488,094
Treasury shares (in shares)					21,976,200
CECONY | Common Stock
Schedule of Capitalization [Line Items]
Common stock, shares outstanding (in shares)				235,488,094	235,000,000	235,488,094	235,000,000			235,000,000
Subsequent Event | Forward Contract | Common Stock
Schedule of Capitalization [Line Items]
Shares issued (in shares)	1,050,000
Value of shares issued	$ 88