Investment in ProLiance Holdings, LLC (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Ownership percentage	61.00%
Governance and voting rights	50.00%
Summarized balance sheet information [Abstract]
Total investment in Proliance included in Investments in unconsolidated affiliates and other nonutility investments	$ 19.7	$ 20.4
ProLiance Holdings, LLC
Summarized balance sheet information [Abstract]
Cash	0.8
Investment in LA Storage	22.4
Total investment in ProLiance	23.2
ProLiance Holdings, LLC \| Investments in unconsolidated affiliates
Summarized balance sheet information [Abstract]
Total investment in Proliance included in Investments in unconsolidated affiliates and other nonutility investments	18.8
ProLiance Holdings, LLC \| Other nonutility investments
Summarized balance sheet information [Abstract]
Total investment in Proliance included in Investments in unconsolidated affiliates and other nonutility investments	$ 4.4
LA Storage
Summarized balance sheet information [Abstract]
Combined Joint Venture Ownership Percentage	100.00%
LA Storage \| Affiliated Entity
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
LA Storage \| ProLiance Holdings, LLC
Summarized balance sheet information [Abstract]
ProLiance's investment in joint venture	$ 36.8	$ 36.7

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_EquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Equity method investment, combined joint venture ownership percentage

+ References

No definition available.

+ Details

Name:	vvc_CombinedJointVentureOwnershipPercentage
Namespace Prefix:	vvc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Equity method investment, voting and governance rights

+ References

No definition available.

+ Details

Name:	vvc_EquityMethodInvestmentVotingandGovernanceRights
Namespace Prefix:	vvc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of the storage assets reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	vvc_EquityMethodinvestmentSummarizedFinancialInformationStorageAssets
Namespace Prefix:	vvc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of cash reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	vvc_EquitymethodinvestmentSummarizedFinancialInformationCash
Namespace Prefix:	vvc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Equity method investment, gross investment in equity method investee

+ References

No definition available.

+ Details

Name:	vvc_Equitymethodinvestmentgrossinvestmentinequitymethodinvestee
Namespace Prefix:	vvc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=vvc_ProlianceHoldingsLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=vvc_InvestmentsInUnconsolidatedAffiliatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=vvc_LAStorageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=us-gaap_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=vvc_ProlianceHoldingsLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: