Summary of Significant Accounting Policies and Other Matters - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,604	$ 2,582	$ 5,932	$ 5,819
Total revenues	2,744	2,696	6,258	6,060
Other
Disaggregation of Revenue [Line Items]
Total revenues	140	114	326	241
Clean Energy Businesses | Renewables | Engineering, procurement and construction
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4	9	6	97
CECONY
Disaggregation of Revenue [Line Items]
Total revenues	2,331	2,338	5,371	5,222
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	2,744	2,696	6,258	6,060
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	187	96	317	246
Total revenues	233	158	450	391
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	46	62	133	145
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	171	73	278	205
Total revenues	171	73	278	205
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	16	23	39	41
Total revenues	16	23	39	41
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	46	62	133	145
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	46	62	133	145
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	2,237	2,292	5,177	5,130
Total revenues	2,331	2,338	5,371	5,222
Operating Segments | CECONY | Other
Disaggregation of Revenue [Line Items]
Total revenues	94	46	194	92
Operating Segments | CECONY | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,751	1,771	3,465	3,474
Total revenues	1,833	1,807	3,630	3,536
Operating Segments | CECONY | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	82	36	165	62
Operating Segments | CECONY | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	400	428	1,310	1,252
Total revenues	408	435	1,330	1,276
Operating Segments | CECONY | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	8	7	20	24
Operating Segments | CECONY | Steam
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	86	93	402	404
Total revenues	90	96	411	410
Operating Segments | CECONY | Steam | Other
Disaggregation of Revenue [Line Items]
Total revenues	4	3	9	6
Operating Segments | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	179	193	436	441
Total revenues	179	198	437	445
Operating Segments | O&R | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	5	1	4
Operating Segments | O&R | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	140	146	283	293
Total revenues	138	144	283	293
Operating Segments | O&R | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	(2)	(2)	0	0
Operating Segments | O&R | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	39	47	153	148
Total revenues	41	54	154	152
Operating Segments | O&R | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	2	7	1	4
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Total revenues	0	1	(2)	0
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 1	$ (2)	$ 0