Property, Plant and Equipment (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) MW	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted-average remaining lease term (in years) - finance leases	7 years 6 months
Finance lease right of use assets, gross	$ 179	$ 0
Property plant and equipment and finance lease assets, gross	33,673	32,514
Finance lease right of use assets, accumulated amortization	0	0
Property plant and equipment and finance lease assets, accumulated depreciation and amortization	10,189	10,152
Property, Plant and Equipment, net	23,484	22,362
Finance ROU assets	179	0
Property plant and equipment and finance lease assets, net	23,484	22,362
Depreciation and Amortization [Abstract]
Depreciation	1,024	961	$ 879
Amortization of securitized regulatory assets	213	155	271
Other amortization	79	73	75
Total	1,316	1,189	1,225
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	787	539
Accretion expense	21	16
Revisions in estimate	(67)	232
Ending balance	$ 741	787	539
Houston Electric
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted-average remaining lease term (in years) - finance leases	7 years 6 months
Finance lease right of use assets, gross	$ 179	0
Property plant and equipment and finance lease assets, gross	15,273	13,593
Finance lease right of use assets, accumulated amortization	0	0
Property plant and equipment and finance lease assets, accumulated depreciation and amortization	4,070	3,930
Property, Plant and Equipment, net	11,203	9,663
Finance ROU assets	179	0
Property plant and equipment and finance lease assets, net	11,203	9,663
Depreciation and Amortization [Abstract]
Depreciation	391	368	339
Amortization of securitized regulatory assets	213	155	271
Other amortization	38	37	38
Total	642	560	648
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	43	42
Accretion expense	1	1
Revisions in estimate	(2)	0
Ending balance	42	43	42
CERC Corp
Property, Plant and Equipment, Net, by Type [Abstract]
Property plant and equipment and finance lease assets, gross	7,878	8,972
Property plant and equipment and finance lease assets, accumulated depreciation and amortization	2,115	2,414
Property, Plant and Equipment, net	5,763	6,558
Finance ROU assets	0	0
Property plant and equipment and finance lease assets, net	5,763	6,558
Depreciation and Amortization [Abstract]
Depreciation	311	289	277
Amortization of securitized regulatory assets	0	0	0
Other amortization	15	15	16
Total	326	304	293
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	571	325
Accretion expense	12	11
Revisions in estimate	(93)	235
Ending balance	$ 490	571	$ 325
Electric transmission and distribution
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	36 years
Property, Plant and Equipment, Gross	$ 17,156	15,225
Accumulated Depreciation & Amortization	4,658	4,785
Property, Plant and Equipment, net	$ 12,498	10,440
Electric transmission and distribution | Houston Electric
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	38 years
Property, Plant and Equipment, Gross	$ 13,321	11,911
Accumulated Depreciation & Amortization	3,502	3,396
Property, Plant and Equipment, net	$ 9,819	8,515
Electric generation
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	26 years
Property, Plant and Equipment, Gross	$ 1,807	1,922
Accumulated Depreciation & Amortization	1,179	754
Property, Plant and Equipment, net	$ 628	1,168
Natural gas distribution
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	30 years
Property, Plant and Equipment, Gross	$ 13,578	14,022
Accumulated Depreciation & Amortization	3,981	4,019
Property, Plant and Equipment, net	$ 9,597	10,003
Natural gas distribution | CERC Corp
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	29 years
Property, Plant and Equipment, Gross	$ 7,833	8,928
Accumulated Depreciation & Amortization	2,093	2,392
Property, Plant and Equipment, net	$ 5,740	6,536
Other property
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	16 years
Property, Plant and Equipment, Gross	$ 953	1,345
Accumulated Depreciation & Amortization	371	594
Property, Plant and Equipment, net	$ 582	751
Other property | Houston Electric
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	19 years
Property, Plant and Equipment, Gross	$ 1,773	1,682
Accumulated Depreciation & Amortization	568	534
Property, Plant and Equipment, net	$ 1,205	1,148
Other property | CERC Corp
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	19 years
Property, Plant and Equipment, Gross	$ 45	44
Accumulated Depreciation & Amortization	22	22
Property, Plant and Equipment, net	$ 23	$ 22
SIGECO
Property, Plant and Equipment, Net, by Type [Abstract]
Number of megawatts (in MW) | MW	300
SIGECO's share of cost of Warrick Unit 4	$ 196
SIGECO's share of accumulated depreciation of Warrick Unit 4	$ 154