Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts		$ 1,566	$ 1,649	$ 3,707	$ 3,876
Other	[1]	9	9	35	11
Revenues		1,575	1,658	3,742	3,887
Lease Income		1	1	2	3
Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenues	[2]	720	765	1,358	1,454
Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenues		128	140	257	223
Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		641	673	1,959	2,088
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		86	80	168	122
Reportable Subsegments [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		722	768	1,360	1,458
Other	[1]	(2)	(3)	(2)	(4)
Revenues		720	765	1,358	1,454
Reportable Subsegments [Member] | Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		128	140	257	223	[3]
Other	[1]	0	0	0	0	[3]
Revenues		128	140	257	223	[3]
Reportable Subsegments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		632	663	1,925	2,076	[3]
Other	[1]	9	10	34	12	[3]
Revenues		641	673	1,959	2,088	[3]
Reportable Subsegments [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		84	78	165	119	[3]
Other	[1]	2	2	3	3	[3]
Revenues		86	80	168	122	[3]
Houston Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues		720	765	1,354	1,451
Houston Electric [Member] | Reportable Subsegments [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		722	768	1,360	1,458
Other	[4]	(2)	(3)	(6)	(7)
Revenues		720	765	1,354	1,451
CERC Corp [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		472	515	1,456	1,721
Other	[5]	11	11	38	17
Revenues		483	526	1,494	1,738
CERC Corp [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		480	526	1,488	1,737
CERC Corp [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		3	0	6	1
CERC Corp [Member] | Reportable Subsegments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		470	515	1,451	1,720
Other	[5]	10	11	37	17
Revenues		480	526	1,488	1,737
CERC Corp [Member] | Reportable Subsegments [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		2	0	5	1
Other	[5]	1		1
Revenues		$ 3	$ 0	$ 6	$ 1

[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 $1 million and $1 million for the three months ended June 30, 2020 and 2019, respectively, and $2 million and $3 million for the six months ended June 30, 2020 and 2019, respectively.

[2] CenterPoint Energy’s Houston Electric T&D’s revenues from major external customers are as follows:     Three Months Ended June 30,   Six Months Ended June 30,     2020   2019   2020   2019     (in millions) Affiliates of NRG   $ 174
  $ 165
  $ 330
  $ 316
Affiliates of Vistra Energy Corp.   92
  59
  173
  113

[3] Reflects revenues from Vectren subsidiaries for the period from February 1, 2019 to June 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 or six months ended June 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 or six months ended June 30, 2020 and 2019.