Short-Term Borrowings and Long-term Debt (Details) $ in Millions		9 Months Ended
		Sep. 30, 2019 USD ($) day	Aug. 12, 2019 USD ($)	May 15, 2019 USD ($)	Feb. 08, 2019 USD ($)	[14]	Jan. 15, 2019 USD ($)	Dec. 31, 2018 USD ($)
Acquired Long-term Debt [Abstract]
Accrued interest expense		$ 5
Commercial paper issued in connection with the Merger		$ 764
Number of days until commercial paper maturity | day		60
Line of Credit Facility [Abstract]
Size of credit facility		$ 5,100
Number of days until commercial paper maturity | day		60
VCC [Member]
Line of Credit Facility [Abstract]
Size of credit facility	[1]	$ 200
Credit facility swing line sublimit		40
Letters of credit swing line sublimit		80
Parent Company [Member]
Line of Credit Facility [Abstract]
Size of credit facility		3,300
VUHI [Member]
Line of Credit Facility [Abstract]
Size of credit facility	[2]	400
Credit facility swing line sublimit		10
Letters of credit swing line sublimit		20
Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt		1,708
Houston Electric [Member]
Debt Instruments [Abstract]
General mortgage bonds used as collateral		68						$ 68
Line of Credit Facility [Abstract]
Size of credit facility		300
VUHI [Member]
Acquired Long-term Debt [Abstract]
Intercompany notes payable established as a result of the merger		$ 568
Number of days until commercial paper maturity | day		30
Line of Credit Facility [Abstract]
Number of days until commercial paper maturity | day		30
VCC [Member]
Acquired Long-term Debt [Abstract]
Intercompany notes payable established as a result of the merger		$ 191
Basis spread on LIBOR		70.00%
Line of Credit Facility [Abstract]
Basis spread on LIBOR		70.00%
CERC Corp [Member]
Line of Credit Facility [Abstract]
Size of credit facility		$ 900
Revolving Credit Facility [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		0						0
Revolving Credit Facility [Member] | VCC [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[3]	0
Revolving Credit Facility [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[4]	0						0
Revolving Credit Facility [Member] | VUHI [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[5]	0
Revolving Credit Facility [Member] | Houston Electric [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		0						0
Revolving Credit Facility [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		$ 0						0
Line of Credit [Member] | VCC [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant	[1]	65.00%
Ratio of indebtedness to net capital	[1],[6]	0.571
Line of Credit [Member] | VCC [Member] | London Interbank Offered Rate (LIBOR) [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR	[1],[7]	1.25%
Line of Credit Facility [Abstract]
Basis spread on LIBOR	[1],[7]	1.25%
Line of Credit [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant	[8]	65.00%
Percentage on limitation of debt to total capitalization under covenant amended (in hundredths)		70.00%
Ratio of indebtedness to net capital	[6]	0.586
System restoration costs threshold for increase in permitted debt to EBITDA covenant ratio		$ 100
Consecutive period for system restoration costs to exceed $100 million (in months)		12
Line of Credit [Member] | Parent Company [Member] | London Interbank Offered Rate (LIBOR) [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR	[7]	1.50%
Line of Credit Facility [Abstract]
Basis spread on LIBOR	[7]	1.50%
Line of Credit [Member] | VUHI [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant	[2]	65.00%
Ratio of indebtedness to net capital	[2],[6]	0.529
Line of Credit [Member] | VUHI [Member] | London Interbank Offered Rate (LIBOR) [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR	[2],[7]	1.125%
Line of Credit Facility [Abstract]
Basis spread on LIBOR	[2],[7]	1.125%
Line of Credit [Member] | Houston Electric [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant	[8]	65.00%
Ratio of indebtedness to net capital	[6]	0.487
Line of Credit [Member] | Houston Electric [Member] | London Interbank Offered Rate (LIBOR) [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR	[7]	1.125%
Line of Credit Facility [Abstract]
Basis spread on LIBOR	[7]	1.125%
Line of Credit [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant		65.00%
Ratio of indebtedness to net capital	[6]	0.475
Line of Credit [Member] | CERC Corp [Member] | London Interbank Offered Rate (LIBOR) [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR	[7]	1.25%
Line of Credit Facility [Abstract]
Basis spread on LIBOR	[7]	1.25%
Letter of Credit [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		$ 7						11
Letter of Credit [Member] | VCC [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[3]	0
Letter of Credit [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[4]	6						6
Letter of Credit [Member] | VUHI [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[5]	0
Letter of Credit [Member] | SIGECO [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		21
Letter of Credit [Member] | Houston Electric [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		0						4
Letter of Credit [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		1						1
Commercial Paper [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		1,971						210
Commercial Paper [Member] | VCC [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[3]	$ 0
Weighted average interest rate of debt	[3]	0.00%
Commercial Paper [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[4]	$ 1,383						$ 0
Weighted average interest rate of debt	[4]	2.28%						0.00%
Commercial Paper [Member] | VUHI [Member]
Line of Credit Facility [Abstract]
Long-term line of credit	[5]	$ 278
Weighted average interest rate of debt	[5]	2.30%
Commercial Paper [Member] | Houston Electric [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		$ 0						$ 0
Commercial Paper [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		$ 310						$ 210
Weighted average interest rate of debt		2.28%						2.93%
Long term Debt Excluding ZENS [Member]
Maturities of Long-term Debt [Abstract]
Remaining three months of 2019		$ 69
2020		831
2021		2,761
2022		2,998
2023		713
2024		1,184
2025 and thereafter		$ 6,447
General Mortgage Bonds Due 2049 [Member] | Houston Electric [Member]
Debt Instruments [Abstract]
Principal amount of debt issued							$ 700
Interest rate of debt		4.25%
Acquired Long-term Debt [Abstract]
Interest rate of debt		4.25%
Revolving Credit Facility [Member] | Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt	[9]	$ 0
Variable term rate loan 2 [Member]
Debt Instruments [Abstract]
Interest rate of debt		2.81%
Acquired Long-term Debt [Abstract]
Interest rate of debt		2.81%
Variable term rate loan 2 [Member] | Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt	[10]	$ 200
First Mortgage Bonds [Member] | Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt	[11]	293
Commercial Paper [Member] | Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt	[12]	278
Senior Notes Due Range 2 [Member] | Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt	[13]	637
Senior Notes Due Range 2 [Member] | VUHI [Member]
Acquired Long-term Debt [Abstract]
Long-term debt		532
Senior Notes Due Range 2 [Member] | Indiana Gas [Member]
Acquired Long-term Debt [Abstract]
Long-term debt		96
Senior Notes Due Range 2 [Member] | VCC [Member]
Acquired Long-term Debt [Abstract]
Long-term debt		$ 9
Variable rate term loan [Member]
Debt Instruments [Abstract]
Principal amount of debt issued				$ 1,000	$ 25
Interest rate of debt	[14]	2.88%
Acquired Long-term Debt [Abstract]
Interest rate of debt	[14]	2.88%
Variable rate term loan [Member] | Vectren [Member]
Acquired Long-term Debt [Abstract]
Long-term debt	[15]	$ 300
Senior Notes Due 2024 [Member] | Parent Company [Member]
Debt Instruments [Abstract]
Principal amount of debt issued			$ 500
Interest rate of debt			2.50%
Acquired Long-term Debt [Abstract]
Interest rate of debt			2.50%
Senior Notes Due 2030 [Member]
Debt Instruments [Abstract]
Interest rate of debt			2.95%
Acquired Long-term Debt [Abstract]
Interest rate of debt			2.95%
Senior Notes Due 2030 [Member] | Parent Company [Member]
Debt Instruments [Abstract]
Principal amount of debt issued			$ 400
Senior Notes Due 2049 [Member]
Debt Instruments [Abstract]
Interest rate of debt			3.70%
Acquired Long-term Debt [Abstract]
Interest rate of debt			3.70%
Senior Notes Due 2049 [Member] | Parent Company [Member]
Debt Instruments [Abstract]
Principal amount of debt issued			$ 300
Minimum [Member] | VUHI [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR		70.00%
Line of Credit Facility [Abstract]
Basis spread on LIBOR		70.00%
Minimum [Member] | First Mortgage Bonds [Member] | Vectren [Member]
Debt Instruments [Abstract]
Interest rate of debt		2.375%
Acquired Long-term Debt [Abstract]
Interest rate of debt		2.375%
Minimum [Member] | Senior Notes Due Range 2 [Member] | Vectren [Member]
Debt Instruments [Abstract]
Interest rate of debt		3.33%
Acquired Long-term Debt [Abstract]
Interest rate of debt		3.33%
Maximum [Member] | VUHI [Member]
Acquired Long-term Debt [Abstract]
Basis spread on LIBOR		90.00%
Line of Credit Facility [Abstract]
Basis spread on LIBOR		90.00%
Maximum [Member] | Letter of Credit [Member] | Vectren [Member]
Line of Credit Facility [Abstract]
Long-term line of credit		$ 50
Maximum [Member] | First Mortgage Bonds [Member] | Vectren [Member]
Debt Instruments [Abstract]
Interest rate of debt		6.72%
Acquired Long-term Debt [Abstract]
Interest rate of debt		6.72%
Maximum [Member] | Senior Notes Due Range 2 [Member] | Vectren [Member]
Debt Instruments [Abstract]
Interest rate of debt		7.08%
Acquired Long-term Debt [Abstract]
Interest rate of debt		7.08%

[1] This credit facility was issued by VCC, is guaranteed by Vectren and includes a $40 million swing line sublimit and an $80 million letter of credit sublimit.

[2] This credit facility was issued by VUHI, is guaranteed by SIGECO, Indiana Gas and VEDO and includes a $10 million swing line sublimit and a $20 million letter of credit sublimit. This credit facility backstops VUHI’s commercial paper program.

[3] This credit facility was issued by VCC and is guaranteed by Vectren.

[4] CenterPoint Energy’s outstanding commercial paper generally has maturities of 60 days or less.

[5] This credit facility was issued by VUHI and is guaranteed by SIGECO, Indiana Gas and VEDO.

[6] As defined in the revolving credit facility agreements, excluding Securitization Bonds.

[7] Based on current credit ratings.

[8] For CenterPoint Energy and Houston Electric, the financial covenant limit will temporarily increase from 65% to 70% if Houston Electric experiences damage from a natural disaster in its service territory and CenterPoint Energy certifies to the administrative agent that Houston Electric has incurred system restoration costs reasonably likely to exceed $100 million in a consecutive 12-month period, all or part of which Houston Electric intends to seek to recover through securitization financing. Such temporary increase in the financial covenant would be in effect from the date CenterPoint Energy delivers its certification until the earliest to occur of (i) the completion of the securitization financing, (ii) the first anniversary of CenterPoint Energy’s certification or (iii) the revocation of such certification.

[9] Represents borrowings under the VCC credit facility, which is guaranteed by Vectren.

[10] Issued by VCC and guaranteed by Vectren. As of September 30, 2019, the term loan was fully drawn upon, exclusive of any potential incremental term loans under the related facility’s accordion feature. The term loan’s interest rate is currently priced at one-month LIBOR, plus a credit spread of 70 basis points.

[11] The first mortgage bonds issued by SIGECO subject SIGECO’s properties to a lien under the related mortgage indenture. The first mortgage bonds have stated interest rates that range from 2.375% to 6.72%.

[12] Issued by VUHI with maturities up to 30 days.

[13] Consists of $532 million of senior notes issued by VUHI, $96 million of senior notes issued by Indiana Gas, and $9 million of senior notes issued by VCC. The senior notes have stated interest rates that range from 3.33% to 7.08%. The senior notes issued by VUHI are guaranteed by SIGECO, Indiana Gas and VEDO. The senior notes issued by VCC are guaranteed by Vectren. In connection with the Merger, two of CenterPoint Energy’s acquired wholly-owned subsidiaries, VUHI and VCC, made offers to prepay certain outstanding guaranteed senior notes as required pursuant to certain note purchase agreements previously entered into by VUHI and VCC. In turn, VUHI and VCC borrowed $568 million and $191 million, respectively, from CenterPoint Energy to fund note redemptions effected pursuant to these prepayment offers. To fund these prepayments and payments of approximately $5 million of accrued interest, CenterPoint Energy issued approximately $764 million of commercial paper.

[14] Draw down by VCC on its variable rate term loan.

[15] Issued by VUHI and guaranteed by SIGECO, Indiana Gas and VEDO. As of September 30, 2019, the term loan was fully drawn upon. The term loan’s interest rate is currently priced at one-month LIBOR, plus a credit spread ranging from 70 to 90 basis points depending on credit rating.