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Label Element Value
(Delaware Smid Cap Growth Fund)  
Prospectus: rr_ProspectusTable  
Objective [Heading] rr_ObjectiveHeading

What is the Fund's investment objective?

Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

Delaware Smid Cap Growth Fund seeks long-term capital appreciation.

Expense [Heading] rr_ExpenseHeading

What are the Fund's fees and expenses?

Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales-charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Delaware Investments® Funds. More information about these and other discounts is available from your financial intermediary, in the Fund's prospectus under the section entitled "About your account," and in the Fund's statement of additional information (SAI) under the section entitled "Purchasing Shares."

Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales-charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Delaware Investments® Funds. More information about these and other discounts is available from your financial intermediary, in the Fund's prospectus under the section entitled "About your account," and in the Fund's statement of additional information (SAI) under the section entitled "Purchasing Shares."
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)
Expense Example [Heading] rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 8% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 8.00%
Strategy [Heading] rr_StrategyHeading

What are the Fund's principal investment strategies?

Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests primarily in common stocks of growth-oriented companies that its portfolio managers believe have long-term capital appreciation potential and expect to grow faster than the U.S. economy. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of small-and mid-capitalization companies (80% policy). For purposes of this Fund, small-market capitalization companies are those companies whose market capitalization is similar to the market capitalization of companies in the Russell 2000® Growth Index, and mid-market capitalization companies are those companies whose market capitalization is similar to the market capitalization of companies in the Russell Midcap® Growth Index. The two indices listed above are for purposes of determining range and not for targeting portfolio management. As of Dec. 31, 2014, the Russell 2000 Growth Index had a market capitalization range between $30.69 million and $7.28 billion, and the Russell Midcap Growth Index had a market capitalization range between $274.56 million and $33.59 billion. The market capitalization range for the indices listed above will change on a periodic basis. A company's market capitalization is determined based on its current market capitalization. Russell Investment Group is the source and owner of the trademarks, service marks, and copyrights related to the Russell Indexes. Russell is a trademark of the Russell Investment Group.

Using a bottom-up approach, the portfolio managers seek to select securities of companies that they believe have attractive end market potential, dominant business models, and strong free cash flow generation that are attractively priced compared to intrinsic value of the securities. The portfolio managers also consider a company's operational efficiencies, management's plans for capital allocation, and the company's shareholder orientation. All of these factors give the portfolio managers insight into the outlook for a company, helping them identify companies poised for sustainable free cash flow growth. The portfolio managers believe that sustainable free cash flow growth, if it occurs, may result in price appreciation for the company's stock.

The Fund's 80% policy is nonfundamental and may be changed without shareholder approval. Fund shareholders would be given at least 60 days' notice prior to any such change.
Risk [Heading] rr_RiskHeading

What are the principal risks of investing in the Fund?

Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

Investing in any mutual fund involves the risk that you may lose part or all of the money you invest. Over time, the value of your investment in the Fund will increase and decrease according to changes in the value of the securities in the Fund's portfolio. Principal risks include:

Market risk — The risk that all or a majority of the securities in a certain market — such as the stock or bond market — will decline in value because of factors such as adverse political or economic conditions, future expectations, investor confidence, or heavy institutional selling.

Limited number of stocks risk — The possibility that a single security's increase or decrease in value may have a greater impact on the fund's value and total return because the fund may hold larger positions in fewer securities than other funds.

Company size risk — The risk that investments in small- and/or medium-sized companies may be more volatile than those of larger companies because of limited financial resources or dependence on narrow product lines.

Futures and options risk — The possibility that a fund may experience a loss if it employs an options or futures strategy related to a security or a market index and that security or index moves in the opposite direction from what the portfolio manager anticipated. Futures and options also involve additional expenses (such as the payment of premiums), which could reduce any benefit or increase any loss that a fund gains from using the strategy.

Foreign risk — The risk that foreign securities (particularly in emerging markets) may be adversely affected by political instability, changes in currency exchange rates, inefficient markets and higher transaction costs, foreign economic conditions, the imposition of economic or trade sanctions, or inadequate or different regulatory and accounting standards.

Liquidity risk — The possibility that securities cannot be readily sold within seven days at approximately the price at which a portfolio has valued them.

Counterparty risk — The risk that a counterparty to a derivatives contract (such as a swap, futures, or options contract) or a repurchase agreement may fail to perform its obligations under the contract or agreement due to financial difficulties (such as a bankruptcy or reorganization).

Investments not guaranteed by Delaware Management Company (Manager) or its affiliates — Neither the Manager nor its affiliates noted in this document are authorized deposit-taking institutions for the purposes of the Banking Act 1959 (Commonwealth of Australia). The obligations of these entities do not represent deposits or other liabilities of Macquarie Bank Limited (MBL). MBL does not guarantee or otherwise provide assurance in respect of the obligations of these entities, unless noted otherwise.
Risk Lose Money [Text] rr_RiskLoseMoney Investing in any mutual fund involves the risk that you may lose part or all of the money you invest. Over time, the value of your investment in the Fund will increase and decrease according to changes in the value of the securities in the Fund's portfolio.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

How has Delaware Smid Cap Growth Fund performed?

Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual total returns for the 1-, 5-, and 10-year periods compare with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how it will perform in the future. The returns reflect any expense caps in effect during these periods. The returns would be lower without the expense caps. You may obtain the Fund's most recently available month-end performance by calling 800 523-1918 or by visiting our website at delawareinvestments.com/performance.

Effective Jan. 21, 2010, the Fund transitioned to invest primarily in common stocks of small-to-medium-sized, growth-oriented companies. Small-market capitalization companies are those companies whose market capitalization is similar to the market capitalization of companies in the Russell 2000 Growth Index, and mid-market capitalization companies are those companies whose market capitalization is similar to the market capitalization of companies in the Russell Midcap Growth Index. Prior to this time, the Fund invested primarily in stocks of medium-sized companies whose total market capitalization at the time of investment was within the range of the Russell Midcap Growth Index. The returns reflected in the bar chart may not be indicative of future performance.
Bar Chart [Heading] rr_BarChartHeading

Year-by-year total return (Class A)

Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

As of March. 31, 2016, the Fund's Class A shares had a calendar year-to-date return of 1.16%. During the periods illustrated in this bar chart, Class A's highest quarterly return was 16.94% for the quarter ended March 31, 2012, and its lowest quarterly return was -25.85% for the quarter ended Dec. 31, 2008. The maximum Class A sales charge of 5.75%, which is normally deducted when you purchase shares, is not reflected in the highest/lowest quarterly returns or in the bar chart. If this fee were included, the returns would be less than those shown. The average annual total returns in the table below do include the sales charge.

Class R6 shares have not commenced operations as of the date of this Prospectus and therefore no average annual total returns are shown below for this share class.
Performance Table Heading rr_PerformanceTableHeading

Average annual total returns for periods ended December 31, 2015
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax performance is presented only for Class A shares of the Fund. The after-tax returns for other Fund classes may vary. Actual after-tax returns depend on the investor's individual tax situation and may differ from the returns shown. After-tax returns are not relevant for shares held in tax-deferred investment vehicles such as employer-sponsored 401(k) plans and individual retirement accounts (IRAs). The after-tax returns shown are calculated using the highest individual federal marginal income tax rates in effect during the periods presented and do not reflect the impact of state and local taxes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate The after-tax returns shown are calculated using the highest individual federal marginal income tax rates in effect during the periods presented and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred After-tax returns are not relevant for shares held in tax-deferred investment vehicles such as employer-sponsored 401(k) plans and individual retirement accounts (IRAs).
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund's past performance (before and after taxes) is not necessarily an indication of how it will perform in the future.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax performance is presented only for Class A shares of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress delawareinvestments.com/performance
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 800 523-1918
(Delaware Smid Cap Growth Fund) | Russell 2500™ Growth Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus: rr_ProspectusTable  
1 Year rr_AverageAnnualReturnYear01 (0.19%)
5 Years rr_AverageAnnualReturnYear05 11.43%
10 Years rr_AverageAnnualReturnYear10 8.49%
(Delaware Smid Cap Growth Fund) | Class A  
Prospectus: rr_ProspectusTable  
Maximum sales charge (load) imposed on purchases as a percentage of offering price rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum contingent deferred sales charge (load) as a percentage of original purchase price or redemption price, whichever is lower rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.71%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25% [1]
Other expenses rr_OtherExpensesOverAssets 0.26%
Total annual fund operating expenses rr_ExpensesOverAssets 1.22%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 692
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 940
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,207
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,967
Annual Return 2006 rr_AnnualReturn2006 4.97%
Annual Return 2007 rr_AnnualReturn2007 12.28%
Annual Return 2008 rr_AnnualReturn2008 (41.61%)
Annual Return 2009 rr_AnnualReturn2009 44.49%
Annual Return 2010 rr_AnnualReturn2010 35.03%
Annual Return 2011 rr_AnnualReturn2011 7.96%
Annual Return 2012 rr_AnnualReturn2012 10.38%
Annual Return 2013 rr_AnnualReturn2013 40.84%
Annual Return 2014 rr_AnnualReturn2014 2.81%
Annual Return 2015 rr_AnnualReturn2015 7.05%
Year to Date Return, Label rr_YearToDateReturnLabel As of March. 31, 2016, the Fund's Class A shares had a calendar year-to-date return of 1.16%
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 1.16%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2016
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return was 16.94% for the quarter ended March 31, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 16.94%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2012
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return was -25.85% for the quarter ended Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.85%)
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
1 Year rr_AverageAnnualReturnYear01 0.91%
5 Years rr_AverageAnnualReturnYear05 11.73%
10 Years rr_AverageAnnualReturnYear10 8.86%
(Delaware Smid Cap Growth Fund) | Class A | return after taxes on distributions  
Prospectus: rr_ProspectusTable  
1 Year rr_AverageAnnualReturnYear01 (1.51%)
5 Years rr_AverageAnnualReturnYear05 9.87%
10 Years rr_AverageAnnualReturnYear10 7.30%
(Delaware Smid Cap Growth Fund) | Class A | return after taxes on distributions and sale of Fund shares  
Prospectus: rr_ProspectusTable  
1 Year rr_AverageAnnualReturnYear01 2.52%
5 Years rr_AverageAnnualReturnYear05 9.26%
10 Years rr_AverageAnnualReturnYear10 7.00%
(Delaware Smid Cap Growth Fund) | Class C  
Prospectus: rr_ProspectusTable  
Maximum sales charge (load) imposed on purchases as a percentage of offering price rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum contingent deferred sales charge (load) as a percentage of original purchase price or redemption price, whichever is lower rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [2]
Management fees rr_ManagementFeesOverAssets 0.71%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 0.26%
Total annual fund operating expenses rr_ExpensesOverAssets 1.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 300
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 618
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,062
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,296
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 200
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 618
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,062
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,296
1 Year rr_AverageAnnualReturnYear01 5.33%
5 Years rr_AverageAnnualReturnYear05 12.23%
10 Years rr_AverageAnnualReturnYear10 8.71%
(Delaware Smid Cap Growth Fund) | Class R  
Prospectus: rr_ProspectusTable  
Maximum sales charge (load) imposed on purchases as a percentage of offering price rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum contingent deferred sales charge (load) as a percentage of original purchase price or redemption price, whichever is lower rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.71%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other expenses rr_OtherExpensesOverAssets 0.26%
Total annual fund operating expenses rr_ExpensesOverAssets 1.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 150
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 465
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 803
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,757
1 Year rr_AverageAnnualReturnYear01 6.78%
5 Years rr_AverageAnnualReturnYear05 12.79%
10 Years rr_AverageAnnualReturnYear10 9.26%
(Delaware Smid Cap Growth Fund) | Institutional Class  
Prospectus: rr_ProspectusTable  
Maximum sales charge (load) imposed on purchases as a percentage of offering price rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum contingent deferred sales charge (load) as a percentage of original purchase price or redemption price, whichever is lower rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.71%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.26%
Total annual fund operating expenses rr_ExpensesOverAssets 0.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 99
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 309
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 536
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,190
1 Year rr_AverageAnnualReturnYear01 7.30%
5 Years rr_AverageAnnualReturnYear05 13.35%
10 Years rr_AverageAnnualReturnYear10 9.81%
(Delaware Smid Cap Growth Fund) | Class R6  
Prospectus: rr_ProspectusTable  
Maximum sales charge (load) imposed on purchases as a percentage of offering price rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum contingent deferred sales charge (load) as a percentage of original purchase price or redemption price, whichever is lower rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.71%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.15% [3]
Total annual fund operating expenses rr_ExpensesOverAssets 0.86%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 88
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 274
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 477
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,061
[1] The Fund's Class A shares are subject to a blended rate of 0.10% on all shares acquired prior to June 1, 1992 and 0.25% on all shares acquired on or after June 1, 1992. This method of calculating Class A 12b-1 fees may be discontinued at the sole discretion of the Board of Trustees.
[2] Class C shares redeemed within one year of purchase are subject to a 1.00% contingent deferred sales charge (CDSC).
[3] "Other expenses" for Class R6 are estimated and account for Class R6 shares not being subject to certain expenses as described further in the section of the prospectus entitled "Choosing a share class."