Leases (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Lease, Cost [Abstract]
Operating lease cost		$ 4
Short-term lease cost		5
Total lease cost		9
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets (1)	[1]	67
Lease Right-Of-Use Asset		67	$ 30
Current operating lease liability (2)	[2]	18
Non-current operating lease liability (3)	[3]	$ 49
Weighted-average remaining lease term (in years) - operating leases		5 years 7 months
Weighted-average discount rate - operating leases		3.45%
Operating Lease Liabilities, Payments Due [Abstract]
Remaining nine months of 2019		$ 19
2020		18
2021		12
2022		7
2023		6
2024		3
2025 and beyond		9
Total lease payments		74
Less: Interest		7
Present value of lease liabilities		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		3
Lessor, Operating Lease, Payments to be Received, Next Twelve Months		1
Lessor, Operating Lease, Payments to be Received, Two Years		2
Lessor, Operating Lease, Payments to be Received, Three Years		2
Lessor, Operating Lease, Payments to be Received, Four Years		2
Lessor, Operating Lease, Payments to be Received, Five Years		2
Lessor, Operating Lease, Payments to be Received, Thereafter		10
Lessor, Operating Lease, Payments to be Received		22
Other Information Related to Leases [Abstract]
Operating Lease, Payments		5
Houston Electric [Member]
Lease, Cost [Abstract]
Operating lease cost		0
Short-term lease cost		2
Total lease cost		2
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets (1)	[1]	1
Lease Right-Of-Use Asset		1	1
Current operating lease liability (2)	[2]	0
Non-current operating lease liability (3)	[3]	$ 1
Weighted-average remaining lease term (in years) - operating leases		5 years 7 months
Weighted-average discount rate - operating leases		3.50%
Operating Lease Liabilities, Payments Due [Abstract]
Remaining nine months of 2019		$ 1
2020		0
2021		0
2022		0
2023		0
2024		0
2025 and beyond		0
Total lease payments		1
Less: Interest		0
Present value of lease liabilities		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
Lessor, Operating Lease, Payments to be Received, Next Twelve Months		1
Lessor, Operating Lease, Payments to be Received, Two Years		0
Lessor, Operating Lease, Payments to be Received, Three Years		0
Lessor, Operating Lease, Payments to be Received, Four Years		0
Lessor, Operating Lease, Payments to be Received, Five Years		0
Lessor, Operating Lease, Payments to be Received, Thereafter		0
Lessor, Operating Lease, Payments to be Received		1
Other Information Related to Leases [Abstract]
Operating Lease, Payments		1
CERC Corp [Member]
Lease, Cost [Abstract]
Operating lease cost		1
Short-term lease cost		0
Total lease cost		1
Assets and Liabilities, Lessee [Abstract]
Operating ROU assets (1)	[1]	26
Lease Right-Of-Use Asset		26	$ 27
Current operating lease liability (2)	[2]	4
Non-current operating lease liability (3)	[3]	$ 22
Weighted-average remaining lease term (in years) - operating leases		8 years 2 months
Weighted-average discount rate - operating leases		3.67%
Operating Lease Liabilities, Payments Due [Abstract]
Remaining nine months of 2019		$ 4
2020		5
2021		4
2022		4
2023		3
2024		2
2025 and beyond		9
Total lease payments		31
Less: Interest		5
Present value of lease liabilities		26
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
Lessor, Operating Lease, Payments to be Received, Next Twelve Months		0
Lessor, Operating Lease, Payments to be Received, Two Years		0
Lessor, Operating Lease, Payments to be Received, Three Years		0
Lessor, Operating Lease, Payments to be Received, Four Years		0
Lessor, Operating Lease, Payments to be Received, Five Years		0
Lessor, Operating Lease, Payments to be Received, Thereafter		0
Lessor, Operating Lease, Payments to be Received		0
Other Information Related to Leases [Abstract]
Operating Lease, Payments		$ 1

[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.