Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 293	$ 250	$ 290
Interest cost on projected benefit obligation	549	601	561
Expected return on plan assets	(1,034)	(988)	(1,033)
Recognition of net actuarial loss	699	518	688
Recognition of prior service credit	(16)	(17)	(17)
TOTAL PERIODIC BENEFIT COST	491	364	489
Cost capitalized	(130)	(108)	(127)
Reconciliation to rate level	(250)	(15)	(92)
Total credit recognized	111	241	270
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	274	232	272
Interest cost on projected benefit obligation	515	564	525
Expected return on plan assets	(980)	(936)	(979)
Recognition of net actuarial loss	661	492	651
Recognition of prior service credit	(19)	(19)	(19)
TOTAL PERIODIC BENEFIT COST	451	333	450
Cost capitalized	(123)	(102)	(119)
Reconciliation to rate level	(239)	(12)	(100)
Total credit recognized	$ 89	$ 219	$ 231