Leases (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2019	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Lease, Cost [Abstract]
Operating lease cost		$ 8	$ 19
Short-term lease cost		23	46
Variable lease cost		1	1
Total lease cost		32	66
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets (1)	[1]	67	67
Lease Right-Of-Use Asset		67	67	$ 30
Current operating lease liability (2)	[2]	21	21
Non-current operating lease liability (3)	[3]	$ 46	$ 46
Weighted-average remaining lease term (in years) - operating leases		5 years 2 months 12 days	5 years 2 months 12 days
Weighted-average discount rate - operating leases		3.41%	3.41%
Operating Lease Liabilities, Payments Due [Abstract]
Remaining three months of 2019		$ 6	$ 6
2020		22	22
2021		15	15
2022		9	9
2023		7	7
2024		3	3
2025 and beyond		12	12
Total lease payments		74	74
Less: Interest		7	7
Present value of lease liabilities		67	67
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months					$ 6
Operating Leases, Future Minimum Payments, Due in Two Years					6
Operating Leases, Future Minimum Payments, Due in Three Years					5
Operating Leases, Future Minimum Payments, Due in Four Years					4
Operating Leases, Future Minimum Payments, Due in Five Years					3
Operating Leases, Future Minimum Payments, Due Thereafter					12
Operating Leases, Future Minimum Payments Due	[4]				36
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year		1	1
Lessor, Operating Lease, Payments to be Received, Next Twelve Months		2	2
Lessor, Operating Lease, Payments to be Received, Two Years		2	2
Lessor, Operating Lease, Payments to be Received, Three Years		2	2
Lessor, Operating Lease, Payments to be Received, Four Years		2	2
Lessor, Operating Lease, Payments to be Received, Five Years		2	2
Lessor, Operating Lease, Payments to be Received, Thereafter		10	10
Lessor, Operating Lease, Payments to be Received		21	21
Other Information Related to Leases [Abstract]
Lessee Operating Lease Not Yet Commenced		16	16
Operating Lease, Payments		6	18
Houston Electric [Member]
Lease, Cost [Abstract]
Operating lease cost		0	0
Short-term lease cost		7	12
Variable lease cost		0	0
Total lease cost		7	12
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets (1)	[1]	1	1
Lease Right-Of-Use Asset		1	1	1
Current operating lease liability (2)	[2]	0	0
Non-current operating lease liability (3)	[3]	$ 1	$ 1
Weighted-average remaining lease term (in years) - operating leases		5 years 4 months 24 days	5 years 4 months 24 days
Weighted-average discount rate - operating leases		3.51%	3.51%
Operating Lease Liabilities, Payments Due [Abstract]
Remaining three months of 2019		$ 0	$ 0
2020		1	1
2021		0	0
2022		0	0
2023		0	0
2024		0	0
2025 and beyond		0	0
Total lease payments		1	1
Less: Interest		0	0
Present value of lease liabilities		1	1
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months					1
Operating Leases, Future Minimum Payments, Due in Two Years					0
Operating Leases, Future Minimum Payments, Due in Three Years					0
Operating Leases, Future Minimum Payments, Due in Four Years					0
Operating Leases, Future Minimum Payments, Due in Five Years					0
Operating Leases, Future Minimum Payments, Due Thereafter					0
Operating Leases, Future Minimum Payments Due	[4]				1
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year		0	0
Lessor, Operating Lease, Payments to be Received, Next Twelve Months		1	1
Lessor, Operating Lease, Payments to be Received, Two Years		0	0
Lessor, Operating Lease, Payments to be Received, Three Years		0	0
Lessor, Operating Lease, Payments to be Received, Four Years		0	0
Lessor, Operating Lease, Payments to be Received, Five Years		0	0
Lessor, Operating Lease, Payments to be Received, Thereafter		0	0
Lessor, Operating Lease, Payments to be Received		1	1
Other Information Related to Leases [Abstract]
Operating Lease, Payments		0	1
CERC Corp [Member]
Lease, Cost [Abstract]
Operating lease cost		1	4
Short-term lease cost		0	0
Variable lease cost		0	0
Total lease cost		1	4
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets (1)	[1]	25	25
Lease Right-Of-Use Asset		25	25	$ 27
Current operating lease liability (2)	[2]	4	4
Non-current operating lease liability (3)	[3]	$ 21	$ 21
Weighted-average remaining lease term (in years) - operating leases		7 years 10 months 24 days	7 years 10 months 24 days
Weighted-average discount rate - operating leases		3.66%	3.66%
Operating Lease Liabilities, Payments Due [Abstract]
Remaining three months of 2019		$ 1	$ 1
2020		5	5
2021		5	5
2022		4	4
2023		3	3
2024		2	2
2025 and beyond		9	9
Total lease payments		29	29
Less: Interest		4	4
Present value of lease liabilities		25	25
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months					5
Operating Leases, Future Minimum Payments, Due in Two Years					5
Operating Leases, Future Minimum Payments, Due in Three Years					4
Operating Leases, Future Minimum Payments, Due in Four Years					4
Operating Leases, Future Minimum Payments, Due in Five Years					3
Operating Leases, Future Minimum Payments, Due Thereafter					11
Operating Leases, Future Minimum Payments Due	[4]				$ 32
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year		0	0
Lessor, Operating Lease, Payments to be Received, Next Twelve Months		0	0
Lessor, Operating Lease, Payments to be Received, Two Years		0	0
Lessor, Operating Lease, Payments to be Received, Three Years		0	0
Lessor, Operating Lease, Payments to be Received, Four Years		0	0
Lessor, Operating Lease, Payments to be Received, Five Years		0	0
Lessor, Operating Lease, Payments to be Received, Thereafter		0	0
Lessor, Operating Lease, Payments to be Received		0	0
Other Information Related to Leases [Abstract]
Operating Lease, Payments		$ 2	$ 4

[1] Reported within Other assets in the Condensed Consolidated Balance Sheets.

[2] Reported within Current other liabilities in the Condensed Consolidated Balance Sheets.

[3] Reported within Other liabilities in the Condensed Consolidated Balance Sheets.

[4] The Merger was completed on February 1, 2019. As such, these amounts are exclusive of Vectren’s leases.