Income Tax - Schedule of Differences on Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred tax liabilities:
Property basis differences	$ 8,542	$ 8,770
Regulatory Assets:
System peak reduction and energy efficiency programs	297	220
Environmental remediation costs	310	278
Other regulatory assets	632	561
Unrecognized pension and other postretirement costs	0	22
Pensions and retiree benefits – asset	918	917
Operating lease right-of-use asset	154	230
Equity investments	0	26
Total deferred tax liabilities	10,853	11,024
Deferred tax assets:
Unrecognized pension and other postretirement costs	265	447
Future income tax	427	489
Other regulatory liabilities	844	860
Tax credits carryforward	270	767
Loss carryforwards	7	117
Valuation allowance	(7)	(18)
Superfund and other environmental costs	314	280
Operating lease liabilities	154	233
Pensions and retiree benefits – liability	167	162
Asset retirement obligations	146	153
Equity investments	98	0
Other	125	14
Total deferred tax assets	2,810	3,504
Net deferred tax liabilities	8,043	7,520
Unamortized investment tax credits	26	121
Net deferred tax liabilities and unamortized investment tax credits	8,069	7,641
CECONY
Deferred tax liabilities:
Property basis differences	8,001	7,475
Regulatory Assets:
System peak reduction and energy efficiency programs	291	219
Environmental remediation costs	287	254
Other regulatory assets	577	501
Unrecognized pension and other postretirement costs	0	22
Pensions and retiree benefits – asset	894	894
Operating lease right-of-use asset	153	163
Equity investments	0	0
Total deferred tax liabilities	10,203	9,528
Deferred tax assets:
Unrecognized pension and other postretirement costs	244	431
Future income tax	394	454
Other regulatory liabilities	744	739
Tax credits carryforward	0	0
Loss carryforwards	0	24
Valuation allowance	0	0
Superfund and other environmental costs	288	254
Operating lease liabilities	153	162
Pensions and retiree benefits – liability	153	148
Asset retirement obligations	146	140
Equity investments	0	0
Other	108	45
Total deferred tax assets	2,230	2,397
Net deferred tax liabilities	7,973	7,131
Unamortized investment tax credits	11	13
Net deferred tax liabilities and unamortized investment tax credits	$ 7,984	$ 7,144