Borrowing Arrangements - Narrative (Details) - USD ($)	Dec. 15, 2017	Jun. 01, 2016	Mar. 11, 2016	Dec. 31, 2017	Sep. 22, 2017	Sep. 14, 2017	Jul. 14, 2017	Dec. 31, 2016	Jun. 01, 1986
Debt Instrument [Line Items]
Total long-term debt outstanding				$ 1,848,700,000				$ 1,723,700,000
Maturities of long term debt [Abstract]
Debt maturing within 12 months following date of latest balance sheet				100,000,000
Debt maturing within two years following date of latest balance sheet				60,000,000
Debt maturing within three years following date of latest balance sheet				100,000,000
Debt maturing within four years following date of latest balance sheet				55,000,000
Debt maturing within five years following date of latest balance sheet				80,000,000
Debt maturing thereafter 5 years following date of the latest balance sheet				1,444,000,000
Short-term borrowings				$ 249,500,000				194,400,000
Covenants [Abstract]
Debt to consolidated total capitalization - maximum ratio				65.00%
Vectren Capital Corp.
Maturities of long term debt [Abstract]
Long-term debt				$ 260,000,000
Short-term borrowings				70,000,000
Utility Holdings
Maturities of long term debt [Abstract]
Long-term debt				1,200,000,000
Short-term borrowings				180,000,000
Senior Notes | Guaranteed Senior Notes, Series A
Debt Instrument [Line Items]
Principal amount of notes							$ 100,000,000
Fixed rate stated percentage							3.26%
Senior Notes | Guaranteed Senior Notes, Series B
Debt Instrument [Line Items]
Principal amount of notes							$ 100,000,000
Fixed rate stated percentage							3.93%
Variable Rate Tax-Exempt Bonds | SIGECO
Debt Instrument [Line Items]
Total long-term debt outstanding					$ 41,300,000	$ 152,000,000
Variable Rate Tax-Exempt Bonds | SIGECO | 2013 Series C Notes due 2022
Debt Instrument [Line Items]
Total long-term debt outstanding						4,600,000
Variable Rate Tax-Exempt Bonds | SIGECO | 2013 Series D Notes due 2024
Debt Instrument [Line Items]
Total long-term debt outstanding						22,500,000
Variable Rate Tax-Exempt Bonds | SIGECO | 2013 Series E Notes due 2037
Debt Instrument [Line Items]
Total long-term debt outstanding						$ 22,000,000
Fixed Rate Tax-Exempt Bonds | SIGECO | 2013 Series A Notes due 2038
Debt Instrument [Line Items]
Total long-term debt outstanding					22,200,000
Fixed Rate Tax-Exempt Bonds | SIGECO | 2013 Series B Notes due 2043
Debt Instrument [Line Items]
Total long-term debt outstanding					$ 39,600,000
Fixed Rate Senior Unsecured Notes | Vectren Capital Corp.
Debt Instrument [Line Items]
Total long-term debt outstanding				$ 260,000,000				335,000,000
Fixed Rate Senior Unsecured Notes | Vectren Capital Corp. | 2017, 3.48%
Debt Instrument [Line Items]
Fixed rate stated percentage	3.48%			3.48%
Total long-term debt outstanding				$ 0				75,000,000
Extinguishment of debt, amount	$ 75,000,000
Fixed Rate Senior Unsecured Notes | Vectren Capital Corp. | 2016, 6.92%
Debt Instrument [Line Items]
Fixed rate stated percentage			6.92%
Extinguishment of debt, amount			$ 60,000,000
Fixed Rate Senior Unsecured Notes | Utility Holdings
Debt Instrument [Line Items]
Total long-term debt outstanding				1,200,000,000				1,000,000,000
First Mortgage Bonds | SIGECO
Debt Instrument [Line Items]
Total long-term debt outstanding				$ 292,700,000				$ 292,700,000
Future long term debt sinking fund fund requirements and maturities [Abstract]
Annual sinking fund requirement fixed percentage				1.00%
Utility plant remaining unfunded under mortgage indenture				$ 1,500,000,000
Gross utility plant balance subject to the mortgage indenture				3,400,000,000
First Mortgage Bonds | SIGECO | 2016, 1986 Series, 8.875%
Debt Instrument [Line Items]
Fixed rate stated percentage		8.875%
Extinguishment of debt, amount		$ 13,000,000
Debt issuance									$ 25,000,000
First Mortgage Bonds | SIGECO | Bonds Subject to Mandatory Tender in 2017
Debt Instrument [Line Items]
Mandatory tenders				124,000,000
First Mortgage Bonds | SIGECO | Bond Subject To Mandatory Tender In 2020
Debt Instrument [Line Items]
Mandatory tenders				38,200,000
First Mortgage Bonds | SIGECO | Bond Subject To Mandatory Tender In 2023
Debt Instrument [Line Items]
Mandatory tenders				85,800,000
First Mortgage Bonds | SIGECO | Options callable in 2017
Debt Instrument [Line Items]
Mandatory tenders				84,100,000
First Mortgage Bonds | SIGECO | Options callable in 2018
Debt Instrument [Line Items]
Mandatory tenders				61,800,000
First Mortgage Bonds | SIGECO | Options callable in 2019
Debt Instrument [Line Items]
Mandatory tenders				$ 22,300,000