Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts		$ 1,610	$ 1,644	$ 5,317	$ 5,520
Other	[1]	12	14	47	25
Revenues		1,622	1,658	5,364	5,545
Lease Income		2	4	4	5
Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenues	[2]	828	859	2,186	2,313
Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenues		157	165	414	388
Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		560	541	2,519	2,629
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		77	93	245	215
Reportable Subsegments [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		828	861	2,188	2,319
Other	[1]	0	(2)	(2)	(6)
Revenues		828	859	2,186	2,313
Reportable Subsegments [Member] | Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		157	165	414	388	[3]
Other	[1]	0	0	0	0	[3]
Revenues		157	165	414	388	[3]
Reportable Subsegments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		550	527	2,475	2,603	[3]
Other	[1]	10	14	44	26	[3]
Revenues		560	541	2,519	2,629	[3]
Reportable Subsegments [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		75	91	240	210	[3]
Other	[1]	2	2	5	5	[3]
Revenues		77	93	245	215	[3]
Houston Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues		828	859	2,182	2,310
Houston Electric [Member] | Reportable Subsegments [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		828	861	2,188	2,319
Other	[4]	0	(2)	(6)	(9)
Revenues		828	859	2,182	2,310
CERC Corp [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		417	408	1,873	2,129
Other	[5]	9	12	47	29
Revenues		426	420	1,920	2,158
CERC Corp [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		422	415	1,910	2,152
CERC Corp [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		4	5	10	6
CERC Corp [Member] | Reportable Subsegments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		414	403	1,865	2,123
Other	[5]	8	12	45	29
Revenues		422	415	1,910	2,152
CERC Corp [Member] | Reportable Subsegments [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		3	5	8	6
Other	[5]	1	0	2	0
Revenues		$ 4	$ 5	$ 10	$ 6

[1] Primarily consists of income from ARPs, weather hedge gains (losses) and leases. ARPs are contracts between the utility and its regulators, not between the utility and a customer. The Registrants recognize ARP revenue as other revenues when the regulator-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period. Total lease income was $2 million and $4 million for the three months ended September 30, 2020 and 2019, respectively, and $4 million and $5 million for the nine months ended September 30, 2020 and 2019, respectively.

[2] Houston Electric T&D’s revenues from major external customers are as follows (CenterPoint Energy and Houston Electric): Three Months Ended September 30,Nine Months Ended September 30,2020201920202019(in millions)Affiliates of NRG$243 $231 $573 $547 Affiliates of Vistra Energy Corp.128 83 301 196 

[3] Reflects revenues from Vectren subsidiaries for the period from February 1, 2019 to September 30, 2019.

[4] Primarily consists of income from ARPs, weather hedge gains (losses) and leases. ARPs are contracts between the utility and its regulators, not between the utility and a customer. The Registrants recognize ARP revenue as other revenues when the regulator-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period. Lease income was not significant for the three and nine months ended September 30, 2020 and 2019.

[5] Primarily consists of income from ARPs, weather hedge gains (losses) and leases. ARPs are contracts between the utility and its regulators, not between the utility and a customer. The Registrants recognize ARP revenue as other revenues when the regulator-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period. Lease income was not significant for the three and nine months ended September 30, 2020 and 2019.