Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts		$ 2,056	$ 1,449	$ 4,595		$ 3,575
Derivative income (loss)		768	782	1,844		1,885
Other	[1]	2	(18)	(8)		(54)
Revenues		2,798	2,186	6,329		5,341
Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenues	[2]	765	854	1,454		1,605
Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenues		140	0	223		0
Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		650	487	2,039		1,630
Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenues		838	841	2,020		2,098
Infrastructure Services [Member]
Disaggregation of Revenue [Line Items]
Revenues		325	0	471		0
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		80	4	122		8
Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenues		(28)	(27)	(102)		(65)
Intersegment Eliminations [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenues		0	0	0		0
Intersegment Eliminations [Member] | Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenues		0	0	0		0
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		(10)	(8)	(20)		(18)
Intersegment Eliminations [Member] | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenues		(17)	(19)	(81)		(47)
Intersegment Eliminations [Member] | Infrastructure Services [Member]
Disaggregation of Revenue [Line Items]
Revenues		(1)	0	(1)		0
Intersegment Eliminations [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		0	0	0		0
Reportable Subsegments [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[3]	768	860	1,458		1,621
Derivative income (loss)	[3]	0	0	3		(4)
Other	[1],[3]	(3)	(6)	(7)		(12)
Revenues	[3]	765	854	1,454		1,605
Reportable Subsegments [Member] | Indiana Electric Integrated [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[3]	140	0	223	[4]	0
Derivative income (loss)	[3]	0	0	0	[4]	0
Other	[1],[3]	0	0	0	[4]	0
Revenues	[3]	140	0	223	[4]	0
Reportable Subsegments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[3]	657	509	2,063	[4]	1,695
Derivative income (loss)	[3]	0	0	0	[4]	0
Other	[1],[3]	3	(14)	(4)	[4]	(47)
Revenues	[3]	650	487	2,039	[4]	1,630
Reportable Subsegments [Member] | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[5]	87	78	260		256
Derivative income (loss)	[5]	768	782	1,841		1,889
Other	[1],[5]	0	0	0		0
Revenues	[5]	838	841	2,020		2,098
Reportable Subsegments [Member] | Infrastructure Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[5]	326	0	472	[4]	0
Derivative income (loss)	[5]	0	0	0	[4]	0
Other	[1],[5]	0	0	0	[4]	0
Revenues	[5]	325	0	471	[4]	0
Reportable Subsegments [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[5]	78	2	119	[4]	3
Derivative income (loss)	[5]	0	0	0	[4]	0
Other	[1],[5]	2	2	3	[4]	5
Revenues	[5]	80	4	122	[4]	8
Reportable Subsegments [Member] | Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[3]		(8)			(18)
Derivative income (loss)	[5]	(17)	(19)	(81)		(47)
Revenues		(28)	(27)	(102)		(65)
Reportable Subsegments [Member] | Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[3]	(10)		(20)	[4]
Reportable Subsegments [Member] | Intersegment Eliminations [Member] | Infrastructure Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[5]	(1)		(1)	[4]
Houston Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues		765	854	1,451		1,609
Houston Electric [Member] | Reportable Subsegments [Member] | Houston Electric T&D [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		768	860	1,458		1,621
Other	[6]	(3)	(6)	(7)		(12)
Revenues		765	854	1,451		1,609
CERC Corp [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts		597	587	1,969		1,951
Derivative income (loss)		768	782	1,841		1,889
Other	[7]	3	(14)	0		(47)
Revenues		1,342	1,328	3,710		3,728
CERC Corp [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		503	487	1,688		1,630
CERC Corp [Member] | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenues		839	841	2,021		2,098
CERC Corp [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		0	0	1		0
CERC Corp [Member] | Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenues		(26)	(27)	(100)		(65)
CERC Corp [Member] | Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues		(10)	(8)	(20)		(18)
CERC Corp [Member] | Intersegment Eliminations [Member] | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenues		(16)	(19)	(80)		(47)
CERC Corp [Member] | Intersegment Eliminations [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues		0	0	0		0
CERC Corp [Member] | Reportable Subsegments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[8]	510	509	1,708		1,695
Derivative income (loss)	[8]	0	0	0		0
Other	[7],[8]	3	(14)	0		(47)
Revenues	[8]	503	487	1,688		1,630
CERC Corp [Member] | Reportable Subsegments [Member] | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[9]	87	78	260		256
Derivative income (loss)	[9]	768	782	1,841		1,889
Other	[7],[9]	0	0	0		0
Revenues	[9]	839	841	2,021		2,098
CERC Corp [Member] | Reportable Subsegments [Member] | Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[9]	0	0	1		0
Derivative income (loss)	[9]	0	0	0		0
Other	[7],[9]	0	0	0		0
Revenues	[9]	0	0	1		0
CERC Corp [Member] | Reportable Subsegments [Member] | Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts	[8]	(10)	(8)	(20)		(18)
Derivative income (loss)	[9]	(16)	(19)	(80)		(47)
Revenues		$ (26)	$ (27)	$ (100)		$ (65)

[1] Primarily consists of income from ARPs 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.

[2] Houston Electric T&D revenues from major external customers are as follows:     Three Months Ended June 30,   Six Months Ended June 30,     2019   2018   2019   2018     (in millions) Affiliates of NRG   $ 165
  $ 169
  $ 316
  $ 330
Affiliates of Vistra Energy Corp.   59
  59
  113
  113

[3] Reflected in Utility revenues in the Condensed Statements of Consolidated Income

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

[5] Reflected in Non-utility revenues in the Condensed Statements of Consolidated Income.

[6] Primarily consists of income from ARPs 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.

[7] Primarily consists of income from ARPs 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.

[8] Reflected in Utility revenues in the Condensed Statements of Consolidated Income.

[9] Reflected in Non-utility revenues in the Condensed Statements of Consolidated Income.