Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 250	$ 290	$ 263
Interest cost on projected benefit obligation	601	561	591
Expected return on plan assets	(988)	(1,033)	(968)
Recognition of net actuarial loss	518	688	595
Recognition of prior service cost/(credit)	(17)	(17)	(17)
TOTAL PERIODIC BENEFIT COST	364	489	464
Cost capitalized	(108)	(127)	(181)
Reconciliation to rate level	(15)	(92)	(34)
Total credit recognized	241	270	249
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	232	272	246
Interest cost on projected benefit obligation	564	525	554
Expected return on plan assets	(936)	(979)	(917)
Recognition of net actuarial loss	492	651	563
Recognition of prior service cost/(credit)	(19)	(19)	(19)
TOTAL PERIODIC BENEFIT COST	333	450	427
Cost capitalized	(102)	(119)	(169)
Reconciliation to rate level	(12)	(100)	(41)
Total credit recognized	$ 219	$ 231	$ 217