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Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

The High-Yield Bond Portfolio
Objective [Heading] rr_ObjectiveHeading

What is the Portfolio’s investment objective?
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The High-Yield Bond Portfolio seeks high total return.
Expense [Heading] rr_ExpenseHeading

What are the Portfolio’s fees and expenses? 
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio.
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

Annual portfolio operating expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

Feb. 27, 2015
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

Portfolio turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Portfolio 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 Portfolio shares are held in a taxable account. These costs, which are not reflected in annual Portfolio operating expenses or in the example, affect the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 90% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 90.00%
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 Portfolio with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Portfolio 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 reflects the Manager’s fee waivers and expense reimbursements for the 1-year period and the total operating expenses without waivers for years 2 through 10. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

What are the Portfolio’s principal investment strategies? 
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Portfolio will primarily invest its assets at the time of purchase in: (1) below investment grade corporate bonds rated BB or lower by S&P or similarly rated by another NRSRO; (2) securities issued or guaranteed by the U.S. government, its agencies or instrumentalities; or (3) commercial paper of companies rated A-1 or A-2 by S&P or rated P-1 or P-2 by Moody’s or that may be unrated but considered to be of comparable quality. Of these categories of securities, we anticipate investing primarily in corporate bonds. The Portfolio may also invest in income-producing securities, including common stocks and preferred stocks, some of which may have convertible features or attached warrants and that may be speculative. The Portfolio may invest up to 25% of its total assets in securities of issuers domiciled in foreign countries. The Portfolio may hold cash or invest in short-term debt securities and other money market instruments when, in our opinion, such holdings are prudent given then prevailing market conditions. Except when we believe a temporary defensive approach is appropriate, the Portfolio normally will not hold more than 5% of its total assets in cash or such short-term investments.

 

Under normal circumstances, the Portfolio will invest at least 80% of its net assets, plus any borrowings for investment purposes, in high yield, fixed income securities (80% Policy). The Portfolio’s 80% Policy may be changed without shareholder approval. However, shareholders will be given notice at least 60 days prior to any such change.

 

High yield, fixed income securities, or high yield bonds, are generally considered to be those rated lower than BBB- by S&P and lower than Baa3 by Moody’s, or similarly rated by another NRSRO. The Portfolio will generally focus its investments on bonds in the BB/Ba or B/B ratings categories and in unrated bonds of similar quality.

 

From time to time, the Portfolio may acquire zero-coupon bonds and, to a lesser extent, pay-in-kind (PIK) bonds; however, the Portfolio generally does not purchase a substantial amount of these securities.

 

With respect to U.S. government securities, the Portfolio may invest only in securities issued or guaranteed as to the payment of principal and interest by the U.S. government, and those of its agencies or instrumentalities that are backed by the full faith and credit of the United States.

 

We do not normally intend to respond to short-term market fluctuations or to acquire securities for the purpose of short-term trading; however, we may take advantage of short-term opportunities that are consistent with the Portfolio’s investment objective.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration

Under normal circumstances, the Portfolio will invest at least 80% of its net assets, plus any borrowings for investment purposes, in high yield, fixed income securities (80% Policy). The Portfolio’s 80% Policy may be changed without shareholder approval. However, shareholders will be given notice at least 60 days prior to any such change.
Risk [Heading] rr_RiskHeading

What are the principal risks of investing in the Portfolio? 
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 Portfolio will increase and decrease according to changes in the value of the securities in its portfolio. Principal risks include:

 

Risk Definition
Investment not guaranteed by
the Manager or its affiliates		 Investments in the Portfolio are not and will not be deposits with or liabilities of Macquarie Bank Limited ABN 46 008 583 542 and its holding companies, including their subsidiaries or related companies (Macquarie Group), and are subject to investment risk, including possible delays in repayment and loss of income and capital invested. No Macquarie Group company guarantees or will guarantee the performance of the Portfolio, the repayment of capital from the Portfolio, or any particular rate of return.
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.
High yield risk The risk that high yield securities, commonly known as “junk bonds,” are subject to reduced creditworthiness of issuers; increased risk of default and a more limited and less liquid secondary market than higher rated securities; and greater price volatility and risk of loss of income and principal than are higher rated securities because they are rated below investment grade. High yield bonds are sometimes issued by municipalities with less financial strength and therefore less ability to make projected debt payments on the bonds.
Credit risk The risk that an issuer of a debt security, including a governmental issuer, or an entity that insures a bond may be unable to make interest payments and repay principal in a timely manner.
Interest rate risk The risk that securities will decrease in value if interest rates rise. The risk is generally associated with bonds; however, because companies in the real estate sector and smaller companies often borrow money to finance their operations, they may be adversely affected by rising interest rates.
Bank loans and other
indebtedness risk		 The risk that the portfolio will not receive payment of principal, interest, and other amounts due in connection with these investments and will depend primarily on the financial condition of the borrower and the lending institution.
Foreign risk The risk that foreign securities (particularly in emerging markets) may be adversely affected by political instability, inefficient markets and higher transaction costs, changes in currency exchange rates, foreign economic conditions, or inadequate or different regulatory and accounting standards.
Currency risk The risk that the value of a portfolio’s investments may be negatively affected by changes in foreign currency exchange rates.
Foreign government/
supranational risk		 The risk that a foreign government or government-related issuer may be unable to make timely payments on its external debt obligations.
Derivatives risk Derivative contracts, such as options, futures, and swaps, may involve additional expenses (such as the payment of premiums) and are subject to significant loss if a security or a securities index to which a derivative contract is associated moves in the opposite direction from what the portfolio manager anticipated. Derivative contracts are also subject to the risk that the counterparty may fail to perform its obligations under the contract due to financial difficulties (such as a bankruptcy or reorganization).
Liquidity risk The possibility that securities cannot be readily sold within seven days at approximately the price at which a portfolio has valued them.
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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution

Investments in the Portfolio are not and will not be deposits with or liabilities of Macquarie Bank Limited ABN 46 008 583 542 and its holding companies, including their subsidiaries or related companies (Macquarie Group), and are subject to investment risk, including possible delays in repayment and loss of income and capital invested. No Macquarie Group company guarantees or will guarantee the performance of the Portfolio, the repayment of capital from the Portfolio, or any particular rate of return.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

How has The High-Yield Bond Portfolio performed?
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio’s performance from year to year and by showing how the Portfolio’s average annual total returns for the 1-, 5-, and 10-year periods compare with those of a broad measure of market performance. The Portfolio’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 Portfolio’s most recently available month-end performance by calling 800 231-8002 or by visiting our website at delawareinvestments.com/institutional.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio’s performance from year to year and by showing how the Portfolio’s average annual total returns for the 1-, 5-, and 10-year periods compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone

800 231-8002
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress

delawareinvestments.com/institutional
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture

The Portfolio’s past performance (before and after taxes) is not necessarily an indication of how it will perform in the future.
Bar Chart [Heading] rr_BarChartHeading

Year-by-year total return (The High-Yield Bond Portfolio)      
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the periods illustrated in this bar chart, The High-Yield Bond Portfolio’s highest quarterly return was 21.06% for the quarter ended June 30, 2009 and its lowest quarterly return was -17.17% for the quarter ended Dec. 31, 2008.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel

highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.06%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel

lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (17.17%)
Performance Table Heading rr_PerformanceTableHeading

Average annual total returns for periods ended December 31, 2013
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or 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 Portfolio’s lifetime 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 Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

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 Portfolio’s lifetime and do not reflect the impact of state and local taxes.
DPT CLASS
  
Risk/Return: rr_RiskReturnAbstract  
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.45% [1]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.12%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.57%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [1]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 183
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 318
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 714
Annual Return 2004 rr_AnnualReturn2004 17.37%
Annual Return 2005 rr_AnnualReturn2005 2.97%
Annual Return 2006 rr_AnnualReturn2006 12.43%
Annual Return 2007 rr_AnnualReturn2007 2.19%
Annual Return 2008 rr_AnnualReturn2008 (24.51%)
Annual Return 2009 rr_AnnualReturn2009 54.70%
Annual Return 2010 rr_AnnualReturn2010 17.04%
Annual Return 2011 rr_AnnualReturn2011 3.43%
Annual Return 2012 rr_AnnualReturn2012 17.78%
Annual Return 2013 rr_AnnualReturn2013 9.21%
1 Year rr_AverageAnnualReturnYear01 9.21%
5 Years rr_AverageAnnualReturnYear05 19.22%
10 Years rr_AverageAnnualReturnYear10 9.70%
BofA Merrill Lynch U.S. High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 7.41%
5 Years rr_AverageAnnualReturnYear05 18.70%
10 Years rr_AverageAnnualReturnYear10 8.46%
Return after taxes on distributions | DPT CLASS
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 6.28%
5 Years rr_AverageAnnualReturnYear05 16.15%
10 Years rr_AverageAnnualReturnYear10 6.66%
Return after taxes on distributions and sale of Portfolio shares | DPT CLASS
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 5.20%
5 Years rr_AverageAnnualReturnYear05 14.23%
10 Years rr_AverageAnnualReturnYear10 6.34%
[1] The Portfolio's investment manager, Delaware Management Company (Manager), is contractually waiving its investment advisory fees and/or paying Portfolio expenses (excluding any 12b-1 fees, taxes, interest, short sale and dividend interest expenses, brokerage fees, certain insurance costs, acquired fund fees and expenses, and nonroutine expenses or costs, including, but not limited to, those relating to reorganizations, litigation, conducting shareholder meetings, and liquidations) to the extent necessary to prevent total annual portfolio operating expenses from exceeding 0.59% of the Portfolio's average daily net assets from Feb. 27, 2014 through Feb. 27, 2015. These waivers and reimbursements may only be terminated by agreement of the Manager and the Portfolio.