Borrowing Arrangements - Short-Term Borrowings (Details) - USD ($)		12 Months Ended
	Jul. 14, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-term borrowings [Abstract]
Balance outstanding, as of year end		$ 249,500,000	$ 194,400,000
Utility Group
Short-term borrowings [Abstract]
Short term borrowings available		220,000,000
Balance outstanding, as of year end		$ 179,500,000	$ 194,400,000	$ 14,500,000
Weighted average interest rate, as of year end		1.92%	1.05%	0.55%
Balance outstanding, annual average		$ 172,400,000	$ 59,800,000	$ 53,800,000
Weighted average interest rate, annual average (in hundredths)		1.30%	0.71%	0.38%
Maximum Month End Balance Outstanding		$ 238,700,000	$ 194,400,000	$ 121,500,000
Nonutility Group
Short-term borrowings [Abstract]
Short term borrowings available		130,000,000
Balance outstanding, as of year end		$ 70,000,000	0	0
Weighted average interest rate, as of year end		2.68%
Balance outstanding, annual average		$ 12,200,000	$ 200,000	$ 24,800,000
Weighted average interest rate, annual average (in hundredths)		2.44%	1.60%	1.33%
Maximum Month End Balance Outstanding		$ 70,000,000	$ 6,300,000	$ 69,100,000
Line of Credit | Revolving Credit Facility
Short-term borrowings [Abstract]
Short-term borrowing capacity	$ 600,000,000
Vectren Utility Holdings Inc | Line of Credit | VUHI Credit Agreement | Revolving Credit Facility
Short-term borrowings [Abstract]
Short-term borrowing capacity	400,000,000
Increase (decrease) of credit facility	50,000,000
Vectren Utility Holdings Inc | Line of Credit | VUHI Credit Agreement | Bridge Loan
Short-term borrowings [Abstract]
Short-term borrowing capacity	10,000,000
Vectren Utility Holdings Inc | Line of Credit | VUHI Credit Agreement | Letter of Credit
Short-term borrowings [Abstract]
Short-term borrowing capacity	20,000,000
Vectren Capital Corp.
Short-term borrowings [Abstract]
Balance outstanding, as of year end		$ 70,000,000
Vectren Capital Corp. | Line of Credit | Vectren Capital Credit Agreement | Revolving Credit Facility
Short-term borrowings [Abstract]
Short-term borrowing capacity	200,000,000
Increase (decrease) of credit facility	(50,000,000)
Vectren Capital Corp. | Line of Credit | Vectren Capital Credit Agreement | Bridge Loan
Short-term borrowings [Abstract]
Short-term borrowing capacity	40,000,000
Vectren Capital Corp. | Line of Credit | Vectren Capital Credit Agreement | Letter of Credit
Short-term borrowings [Abstract]
Short-term borrowing capacity	$ 80,000,000