Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,627	$ 2,604	$ 5,784	$ 5,932
Total revenues	2,719	2,744	5,953	6,258
Other
Disaggregation of Revenue [Line Items]
Total revenues	92	140	169	326
Clean Energy Businesses | Renewables | Engineering, procurement and construction
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2	4	4	6
CECONY
Disaggregation of Revenue [Line Items]
Total revenues	2,345	2,331	5,200	5,371
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	2,719	2,744
Operating Segments | Electric
Disaggregation of Revenue [Line Items]
Total revenues			5,953	6,258
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	189	187	314	317
Total revenues	198	233	344	450
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	9	46	30	133
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	178	171	292	278
Total revenues	178	171	292	278
Operating Segments | Clean Energy Businesses | Renewables | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Clean Energy Businesses | Energy services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	11	16	22	39
Total revenues	11	16	22	39
Operating Segments | Clean Energy Businesses | Energy services | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Total revenues	9	46	30	133
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	9	46	30	133
Operating Segments | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	2	2
Total revenues	1	1	2	2
Operating Segments | Con Edison Transmission | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,261	2,237	5,071	5,177
Total revenues	2,345	2,331	5,200	5,371
Operating Segments | CECONY | Other
Disaggregation of Revenue [Line Items]
Total revenues	84	94	129	194
Operating Segments | CECONY | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,781	1,751	3,514	3,465
Total revenues	1,845	1,833	3,616	3,630
Operating Segments | CECONY | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	64	82	102	165
Operating Segments | CECONY | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	399	400	1,232	1,310
Total revenues	416	408	1,250	1,330
Operating Segments | CECONY | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	17	8	18	20
Operating Segments | CECONY | Steam
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	81	86	325	402
Total revenues	84	90	334	411
Operating Segments | CECONY | Steam | Other
Disaggregation of Revenue [Line Items]
Total revenues	3	4	9	9
Operating Segments | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	176	179	397	436
Total revenues	175	179	408	437
Operating Segments | O&R | Other
Disaggregation of Revenue [Line Items]
Total revenues	(1)	0	11	1
Operating Segments | O&R | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	139	140	267	283
Total revenues	138	138	274	283
Operating Segments | O&R | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	(1)	(2)	7	0
Operating Segments | O&R | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	37	39	130	153
Total revenues	37	41	134	154
Operating Segments | O&R | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	2	4	1
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers			0	0
Total revenues	$ 0	$ 0	(1)	(2)
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues			$ (1)	$ (2)