Pioneer Series Trust X

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Registrant Name

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PIONEER SERIES TRUST X

Prospectus Date

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Apr. 01, 2013

Pioneer Absolute Return Credit Fund

Objective, Primary [Text Block]

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Risk/Return [Heading]

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PIONEER ABSOLUTE RETURN CREDIT FUND

Objective [Heading]

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INVESTMENT OBJECTIVES

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A high level of current income.

Objective, Secondary [Text Block]

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Capital appreciation is a secondary objective.

Expense [Heading]

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FEES AND EXPENSES OF THE FUND

Expense Narrative [Text Block]

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This table 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 or your family invest, or agree to invest in the future, at least $100,000 in Class A shares of the Pioneer funds. More information about these and other discounts is available from your investment professional and in the "Sales charges" section of the prospectus beginning on page 42 and the "Sales charges" section of the statement of additional information beginning on page 63.

Shareholder Fees Caption [Text]

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SHAREOWNER FEES
(fees paid directly from your investment)

Operating Expenses Caption [Text]

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ANNUAL FUND 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

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August 1, 2014

Portfolio Turnover [Heading]

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PORTFOLIO TURNOVER

Portfolio Turnover [Text Block]

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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 period from May 2, 2011 (commencement of operations) to March 31, 2012 (fiscal year end), the fund's portfolio turnover rate was 17% of the average value of its portfolio.

Portfolio Turnover, Rate

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17.00%

Expense Breakpoint Discounts [Text]

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You may qualify for sales charge discounts if you or your family invest, or agree to invest in the future, at least $100,000 in Class A shares of the Pioneer funds.

Expense Breakpoint, Minimum Investment Required [Amount]

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100,000

Other Expenses, New Fund, Based on Estimates [Text]

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Other Expenses for Class Z shares are based on estimated amounts for the current fiscal year.

Expense Example [Heading]

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EXAMPLE

Expense Example Narrative [Text Block]

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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 shown and then, except as indicated, redeem all of your shares at the end of those periods. It also assumes that (a) your investment has a 5% return each year and (b) the fund's total annual operating expenses remain the same except for year one (which considers the effect of the expense limitation). Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

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IF YOU REDEEM YOUR SHARES
NUMBER OF YEARS YOU OWN YOUR SHARES

Expense Example, No Redemption, By Year, Caption [Text]

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IF YOU DO NOT REDEEM YOUR SHARES
NUMBER OF YEARS YOU OWN YOUR SHARES

Strategy [Heading]

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PRINCIPAL INVESTMENT STRATEGIES

Strategy Narrative [Text Block]

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The fund selects investments from a broad spectrum of debt securities. The fund is managed using an absolute return approach, which means that it is not managed relative to an index. Accordingly, the fund does not seek to generate returns consistent with broader financial market movements, instead seeking to generate positive total returns over the course of different market environments. Total return is a combination of current income and capital appreciation. As part of its overall strategy, the fund uses derivatives in an effort to limit the effect of market volatility on its portfolio of securities. The fund also may use derivatives for a variety of other hedging and non-hedging purposes.

Normally, the fund invests at least 80% of its net assets (plus the amount of borrowings, if any, for investment purposes) in debt securities. For purposes of satisfying the 80% requirement, the fund may invest in derivative instruments that have economic characteristics similar to such debt securities. The fund has the flexibility to invest in a broad range of issuers and segments of the debt securities markets. The adviser allocates the fund's debt securities among different instruments and segments of the debt markets, based on its outlook for economic, interest rate and political trends. Debt securities may include instruments and obligations of U.S. and non-U.S. corporate and other non-governmental entities, those of U.S. and non-U.S. governmental entities, mortgage-related or mortgage-backed securities (including "sub-prime" mortgages), asset-backed securities, floating rate loans, convertible securities, preferred securities, Treasury Inflation Protected Securities ("TIPS") and other inflation-linked debt securities, subordinated debt securities, event-linked bonds, and funds that invest primarily in debt securities. The fund may invest without limit in debt securities of any credit quality, including those rated below investment grade (known as "junk bonds") or, if unrated, of equivalent credit quality as determined by the fund's investment adviser. The fund's investments in debt securities rated below investment grade may include securities that are in default. The fund may invest in securities of issuers located in emerging markets.

The fund invests in securities with a broad range of maturities and maintains an average portfolio maturity that varies based upon the judgment of the adviser. The fund's investments may have fixed or variable principal payments and all types of interest rate payment and reset terms, including fixed rate, adjustable rate, floating rate, zero coupon, contingent, deferred, payment in kind and auction rate features.

The fund may invest in equity securities, including common stocks, rights, warrants, depositary receipts, exchange-traded funds (ETFs) that invest primarily in equity securities and equity interests in real estate trusts (REITs). The fund may invest in equity securities as a consequence of holding debt of the same issuer or when the adviser believes the securities offer the potential for capital gains or other portfolio management purposes, although equity securities may not pay dividends or contribute to achieving the fund's investment objective of a high level of current income.

The adviser considers both broad economic and issuer specific factors in selecting a portfolio designed to achieve the fund's investment objectives. In assessing the appropriate maturity, rating, sector and country weightings of the fund's portfolio, the adviser considers a variety of factors that are expected to influence economic activity and interest rates. These factors include fundamental economic indicators, such as the rates of economic growth and inflation, Federal Reserve monetary policy and the relative value of the U.S. dollar compared to other currencies. Once the adviser determines the preferable portfolio characteristics, the adviser selects individual securities based upon the terms of the securities (such as yields compared to U.S. Treasuries or comparable issuers), liquidity and rating, sector and issuer diversification. The adviser also employs fundamental quantitative and qualitative research to assess an issuer's credit quality, taking into account financial condition and profitability, future capital needs, potential for change in rating, industry outlook, the competitive environment and management capabilities. In making these portfolio decisions, the adviser relies on the knowledge, experience and judgment of its staff and the staff of its affiliates who have access to a wide variety of research. In selecting among market segments and instruments, the adviser considers the relative value of particular investments. The adviser may sell a portfolio security when it believes the security no longer will contribute to meeting the fund's investment objectives. The adviser makes that determination based on the same criteria it uses to select portfolio securities.

In addition to managing portfolio risk through conventional means, including through in-depth credit analysis and diversification, the adviser employs a disciplined, two-fold derivatives strategy designed to limit the effects of near-term volatility and severe market events. This strategy, which relies on proprietary, quantitative techniques, incorporates the adviser's macroeconomic views as well as its view of quantitative market indicators of financial disruption, such as the volatility of the S&P 500 Index and credit spreads. Credit spreads measure the difference in the yield of higher yielding bond sectors relative to U.S. Treasury bonds. Widening credit spreads can indicate higher levels of uncertainty or distress in financial markets. Over time, the adviser uses derivatives to maintain a "dynamic" hedge against near-term market volatility through exposure to market-, volatility- and/or credit-oriented derivatives, which it may adjust as credit spreads widen and narrow or as other indicators of market volatility change. As a second measure, when indicators signal severe market distress, the investment adviser may employ derivatives techniques designed to help limit the effects of that distress. Derivatives in which the fund may invest for these purposes include equity index futures, futures or swaps based on the Chicago Board of Exchange Volatility Index (VIX), credit default swaps and Treasury futures. The VIX is an index of market sentiment derived from S&P 500 Index option prices that is designed to reflect investors' consensus view of expected stock market volatility over future periods. In combination, the two elements of this strategy are intended to help limit the effect of market volatility on the fund's returns and generate positive returns over time. However, there can be no guarantee that such results will be achieved.

The fund also may use derivatives for a variety of other purposes, including: as a hedge against adverse changes in the market price of securities, interest rates or currency exchange rates; as a substitute for purchasing or selling securities; and to increase the fund's return as a non-hedging strategy that may be considered speculative. The fund may establish, through derivatives, net short positions for individual sectors, markets, currencies or securities, or as a means of adjusting the fund's portfolio duration or other portfolio characteristics. The fund may invest without limit in derivative instruments. The fund may choose not to make use of derivatives for a variety of reasons, and any use may be limited by applicable law and regulations. The fund also may hold cash or other short-term investments.

Risk [Heading]

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PRINCIPAL RISKS OF INVESTING IN THE FUND

Risk Narrative [Text Block]

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You could lose money on your investment in the fund. As with any mutual fund, there is no guarantee that the fund will achieve its objectives.

MARKET RISK. The values of securities held by the fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, inflation, changes in interest or currency rates or adverse investor sentiment. Adverse market conditions may be prolonged and may not have the same impact on all types of securities. The values of securities may fall due to factors affecting a particular issuer, industry or the securities market as a whole. The stock market may perform poorly relative to other investments. (This risk may be greater in the short term.) High public debt in the U.S. and other countries creates ongoing systemic and market risks and policymaking uncertainty. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. Some governmental and non-governmental issuers (notably in Europe) have defaulted on, or been forced to restructure, their debts, and many other issuers have faced difficulties obtaining credit. These market conditions may continue, worsen or spread, including in the U.S., Europe and beyond. Further defaults or restructurings by governments and others of their debt could have additional adverse effects on economies, financial markets and asset valuations around the world. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. Whether or not the fund invests in securities of issuers located in or with significant exposure to countries experiencing economic and financial difficulties, the value and liquidity of the fund's investments may be negatively affected by the countries experiencing these difficulties. In addition, policy and legislative changes in the U.S. and in other countries are affecting many aspects of financial regulation. The impact of these changes, and the practical implications for market participants, may not be fully known for some time. The fund may experience a substantial or complete loss on any individual security.

HIGH YIELD OR "JUNK" BOND RISK. Debt securities that are below investment grade, called "junk bonds," are speculative, have a higher risk of default or are already in default, tend to be less liquid and are more difficult to value than higher grade securities. Junk bonds tend to be volatile and more susceptible to adverse events and negative sentiments.

INTEREST RATE RISK. Interest rates may go up, causing the value of the fund's investments to decline (this risk generally will be greater for securities with longer maturities). Interest rates in the U.S. recently have been historically low.

CREDIT RISK. If an issuer or guarantor of a security held by the fund or a counterparty to a financial contract with the fund defaults on its obligation to pay principal and/or interest, has its credit rating downgraded or is perceived to be less creditworthy, or the credit quality or value of any underlying assets declines, the value of your investment will decline. Credit risk is broadly gauged by the credit ratings of the securities in which the fund invests. However, ratings are only the opinions of the companies issuing them and are not guarantees as to quality. Junk bonds have a higher risk of default or are already in default and are considered speculative.

PREPAYMENT OR CALL RISK. Many issuers have a right to prepay their securities. If interest rates fall, an issuer may exercise this right. If this happens, the fund will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on the prepaid security. The fund also may lose any premium it paid on the security.

EXTENSION RISK. During periods of rising interest rates, the average life of certain types of securities may be extended because of slower than expected principal payments. This may lock in a below market interest rate, increase the security's duration (the estimated period until the security is paid in full) and reduce the value of the security.

LIQUIDITY RISK. Some securities held by the fund may be difficult to sell, or illiquid, particularly during times of market turmoil. Illiquid securities also may be difficult to value. If the fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, the fund may be forced to sell at a loss.

PORTFOLIO SELECTION RISK. The adviser's judgment about the quality, relative yield, relative value or market trends affecting a particular sector or region, market segment, security or about interest rates generally may prove to be incorrect.

U.S. GOVERNMENT AGENCY OBLIGATIONS RISK. The fund invests in obligations issued by agencies and instrumentalities of the U.S. government. Government-sponsored entities such as Federal National Mortgage Association (Fannie Mae), Federal Home Loan Mortgage Corporation (Freddie Mac) and the Federal Home Loan Banks (FHLBs), although chartered or sponsored by Congress, are not funded by congressional appropriations and the debt and mortgage-backed securities issued by them are neither guaranteed nor issued by the U.S. government. Such debt and mortgage-backed securities are subject to the risk of default on the payment of interest and/or principal, similar to debt of private issuers. Although the U.S. government has provided financial support to Fannie Mae and Freddie Mac in the past, there can be no assurance that it will support these or other government-sponsored entities in the future.

MORTGAGE-RELATED AND ASSET-BACKED SECURITIES RISK. The value of mortgage-related and asset-backed securities will be influenced by factors affecting the housing market and the assets underlying such securities. As a result, during periods of declining asset value, difficult or frozen credit markets, swings in interest rates, or deteriorating economic conditions, mortgage-related and asset-backed securities may decline in value, face valuation difficulties, become more volatile and/or become illiquid. Additionally, during such periods and also under normal conditions, these securities are also subject to prepayment and call risk. Some of these securities may receive little or no collateral protection from the underlying assets and are thus subject to the risk of default. The risk of such defaults is generally higher in the case of mortgage-backed investments that include so-called "sub-prime" mortgages. The structure of some of these securities may be complex and there may be less available information than for other types of debt securities. Upon the occurrence of certain triggering events or defaults, the fund may become the holder of underlying assets at a time when those assets may be difficult to sell or may be sold only at a loss.

RISKS OF SUBORDINATED SECURITIES. A holder of securities that are subordinated or "junior" to more senior securities of an issuer is entitled to payment after holders of more senior securities of the issuer. Subordinated securities are more likely to suffer a credit loss than non-subordinated securities of the same issuer, any loss incurred by the subordinated securities is likely to be proportionately greater, and any recovery of interest or principal may take more time. As a result, even a perceived decline in creditworthiness of the issuer is likely to have a greater impact on them.

RISKS OF NON-U.S. INVESTMENTS. Investing in non-U.S. issuers or issuers with significant exposure to foreign markets may involve unique risks compared to investing in securities of U.S. issuers. These risks are more pronounced for issuers in emerging markets or to the extent that the fund invests significantly in one region or country. These risks may include different financial reporting practices and regulatory standards, less liquid trading markets, extreme price volatility, currency risks, changes in economic, political, regulatory and social conditions, sustained economic downturns, financial instability, tax burdens, and investment and repatriation restrictions. Lack of information and less market regulation also may affect the value of these securities. Withholding and other non-U.S. taxes may decrease the fund's return. Non-U.S. issuers may be located in parts of the world that have historically been prone to natural disasters.

INFLATION-LINKED SECURITIES RISK. The principal or interest of inflation-linked securities such as TIPS is adjusted periodically to a specified rate of inflation. The inflation index used may not accurately measure the real rate of inflation. Inflation-linked securities may lose value or interest payments on such securities may decline in the event that the actual rate of inflation is different than the rate of the inflation index.

RISKS OF INVESTING IN EVENT-LINKED BONDS. The return of principal and the payment of interest on "event-linked" bonds are contingent on the non-occurrence of a pre-defined "trigger" event, such as a hurricane or an earthquake of a specific magnitude. If a trigger event, as defined within the terms of an event-linked bond, involves losses or other metrics exceeding a specific magnitude in the geographic region and time period specified therein, the fund may lose a portion or all of its accrued interest and/or principal invested in such event-linked bond. In addition to the specified trigger events, event-linked bonds may expose the fund to other risks, including but not limited to issuer (credit) default, adverse regulatory or jurisdictional interpretations and adverse tax consequences.

RISKS OF INVESTING IN FLOATING RATE LOANS. Floating rate loans and similar investments may be illiquid or less liquid than other investments. The value of collateral, if any, securing a floating rate loan can decline or may be insufficient to meet the issuer's obligations or may be difficult to liquidate. No active trading market may exist for many floating rate loans, and many loans are subject to restrictions on resale. Market quotations for these securities may be volatile and/or subject to large spreads between bid and ask prices. Any secondary market may be subject to irregular trading activity and extended trade settlement periods.

RISK OF INVESTMENT IN OTHER FUNDS. Investing in other investment companies subjects the fund to the risks of investing in the underlying securities or assets held by those funds. When investing in another fund, the fund will bear a pro rata portion of the underlying fund's expenses, in addition to its own expenses.

EQUITY SECURITIES RISK. Equity securities represent an ownership interest in an issuer, rank junior in a company's capital structure to debt securities and consequently may entail greater risk of loss than debt securities. Equity securities are subject to the risk that stock prices may rise and fall in periodic cycles and may perform poorly relative to other investments. This risk may be greater in the short term.

RISKS OF ZERO COUPON BONDS AND PAYMENT IN KIND SECURITIES. Zero coupon bonds and payment in kind securities may be more speculative and may fluctuate more in value than securities which pay income periodically and in cash. In addition, although the fund receives no periodic cash payments on such securities, the fund is deemed for tax purposes to receive income from such securities, which applicable tax rules require the fund to distribute to shareholders. Such distributions may be taxable when distributed to shareholders.

MARKET SEGMENT RISK. To the extent the fund emphasizes, from time to time, investments in a market segment, the fund will be subject to a greater degree to the risks particular to that segment, and may experience greater market fluctuation than a fund without the same focus.

DERIVATIVES RISK. Using derivatives can increase fund losses and reduce opportunities for gains when market prices, interest rates or the derivative instruments themselves behave in a way not anticipated by the fund. Using derivatives may increase the volatility of the fund's net asset value and may not provide the result intended. Derivatives may have a leveraging effect on the fund. Some derivatives have the potential for unlimited loss, regardless of the size of the fund's initial investment. Changes in a derivative's value may not correlate well with the referenced asset or metric. The fund also may have to sell assets at inopportune times to satisfy its obligations. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the fund. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation is not yet fully known and may not be for some time. New regulation of derivatives may make them more costly, may limit their availability, or may otherwise adversely affect their value or performance.

CREDIT DEFAULT SWAP RISK. Credit default swap contracts, a type of derivative instrument, involve special risks and may result in losses to the fund. Credit default swaps may in some cases be illiquid, and they increase credit risk since the fund has exposure to both the issuer of the referenced obligation and the counterparty to the credit default swap. Swaps may be difficult to unwind or terminate. The swap market could be disrupted or limited as a result of recent legislation, and these changes could adversely affect the fund.

LEVERAGING RISK. The value of your investment may be more volatile and other risks tend to be compounded if the fund borrows or uses derivatives or other investments, such as ETFs, that have embedded leverage. Leverage generally magnifies the effect of any increase or decrease in the value of the fund's underlying assets or creates investment risk with respect to a larger pool of assets than the fund would otherwise have, potentially resulting in the loss of all assets. Engaging in such transactions may cause the fund to liquidate positions when it may not be advantageous to do so to satisfy its obligations or meet segregation requirements.

EXPENSE RISK. Your actual costs of investing in the fund may be higher than the expenses shown in "Annual fund operating expenses" for a variety of reasons. For example, expense ratios may be higher than those shown if overall net assets decrease. Net assets are more likely to decrease and fund expense ratios are more likely to increase when markets are volatile.

Please note that there are many other factors that could adversely affect your investment and that could prevent the fund from achieving its goals.

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Lose Money [Text]

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You could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

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An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

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THE FUND'S PAST PERFORMANCE

Performance Narrative [Text Block]

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The bar chart and table indicate the risks and volatility of an investment in the fund by showing how the fund has performed in the past. The bar chart shows changes in the performance of the fund's Class A shares from calendar year to calendar year. The table shows the average annual total returns for each class of the fund over time and compares these returns to the returns of the Bank of America (BofA) Merrill Lynch U.S. Dollar 3-Month LIBOR Index, a broad-based measure of market performance that has characteristics relevant to the fund's investment strategies. You can obtain updated performance information by visiting https://us.pioneerinvestments.com/performance or by calling 1-800-225-6292.

The fund's past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

The bar chart does not reflect any sales charge you may pay when you buy fund shares. If this amount was reflected, returns would be less than those shown.

Performance Information Illustrates Variability of Returns [Text]

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Performance One Year or Less [Text]

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No performance information is presented for Class Z shares in the table because Class Z shares do not have annual returns for at least one calendar year.

Performance Availability Phone [Text]

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1-800-225-6292

Performance Availability Website Address [Text]

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https://us.pioneerinvestments.com/performance

Performance Past Does Not Indicate Future [Text]

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The fund's past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

Bar Chart [Heading]

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ANNUAL RETURN CLASS A SHARES (%)
(Year ended December 31)

Bar Chart Does Not Reflect Sales Loads [Text]

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The bar chart does not reflect any sales charge you may pay when you buy fund shares. If this amount was reflected, returns would be less than those shown.

Bar Chart Closing [Text Block]

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For the period covered by the bar chart:
THE HIGHEST CALENDAR QUARTERLY RETURN WAS 4.54% (01/01/2012 TO 03/31/2012).
THE LOWEST CALENDAR QUARTERLY RETURN WAS 1.00% (04/01/2012 TO 06/30/2012).

Performance Table Heading

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AVERAGE ANNUAL TOTAL RETURN (%)
(for periods ended December 31, 2012)

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on the investor's tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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After-tax returns are shown only for Class A shares. After-tax returns for Class C and Class Y shares shares will vary.

Performance Table Narrative

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor's tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

After-tax returns are shown only for Class A shares. After-tax returns for Class C and Class Y shares shares will vary.

Performance Table Closing [Text Block]

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No performance information is presented for Class Z shares in the table because Class Z shares do not have annual returns for at least one calendar year. The returns for Class Z shares would differ from those of Class A, Class C and Class Y shares because they have different expenses.

Pioneer Absolute Return Credit Fund | CLASS A

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

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rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.50%

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

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none

rr_ManagementFeesOverAssets

0.70%

rr_DistributionAndService12b1FeesOverAssets

0.25%

rr_OtherExpensesOverAssets

0.71%

^[1]

rr_ExpensesOverAssets

1.66%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

(0.46%)

^[2]

Highest Quarterly Return, Label

rr_NetExpensesOverAssets

1.20%

^[2]

rr_ExpenseExampleYear01

567

rr_ExpenseExampleYear03

907

rr_ExpenseExampleYear05

1,270

rr_ExpenseExampleYear10

2,290

rr_ExpenseExampleNoRedemptionYear01

567

rr_ExpenseExampleNoRedemptionYear03

907

rr_ExpenseExampleNoRedemptionYear05

1,270

rr_ExpenseExampleNoRedemptionYear10

2,290

2012

rr_AnnualReturn2012

12.22%

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HIGHEST CALENDAR QUARTERLY RETURN

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

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4.54%

Lowest Quarterly Return, Label

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LOWEST CALENDAR QUARTERLY RETURN

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

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1.00%

rr_AverageAnnualReturnYear01

7.17%

rr_AverageAnnualReturnSinceInception

1.73%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Absolute Return Credit Fund | CLASS C

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

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rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

rr_ManagementFeesOverAssets

0.70%

rr_DistributionAndService12b1FeesOverAssets

1.00%

rr_OtherExpensesOverAssets

0.76%

^[1]

rr_ExpensesOverAssets

2.46%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

(0.36%)

^[2]

rr_NetExpensesOverAssets

2.10%

^[2]

rr_ExpenseExampleYear01

313

rr_ExpenseExampleYear03

732

rr_ExpenseExampleYear05

1,278

rr_ExpenseExampleYear10

2,769

rr_ExpenseExampleNoRedemptionYear01

213

rr_ExpenseExampleNoRedemptionYear03

732

rr_ExpenseExampleNoRedemptionYear05

1,278

rr_ExpenseExampleNoRedemptionYear10

2,769

rr_AverageAnnualReturnYear01

11.40%

rr_AverageAnnualReturnSinceInception

3.69%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Absolute Return Credit Fund | CLASS Y

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

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rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.70%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.60%

^[1]

rr_ExpensesOverAssets

1.30%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

(0.45%)

^[2]

rr_NetExpensesOverAssets

0.85%

^[2]

rr_ExpenseExampleYear01

rr_ExpenseExampleYear03

368

rr_ExpenseExampleYear05

670

rr_ExpenseExampleYear10

1,528

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

368

rr_ExpenseExampleNoRedemptionYear05

670

rr_ExpenseExampleNoRedemptionYear10

1,528

rr_AverageAnnualReturnYear01

12.45%

rr_AverageAnnualReturnSinceInception

5.06%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Absolute Return Credit Fund | CLASS Z

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.70%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.25%

^[1]

rr_ExpensesOverAssets

0.95%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

rr_NetExpensesOverAssets

0.95%

^[2]

rr_ExpenseExampleYear01

rr_ExpenseExampleYear03

303

rr_ExpenseExampleYear05

525

rr_ExpenseExampleYear10

1,166

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

303

rr_ExpenseExampleNoRedemptionYear05

525

rr_ExpenseExampleNoRedemptionYear10

1,166

Pioneer Absolute Return Credit Fund | Return after taxes on distributions | CLASS A

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

5.09%

rr_AverageAnnualReturnSinceInception

(0.05%)

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Absolute Return Credit Fund | Return after taxes on distributions and sale of shares | CLASS A

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

4.60%

rr_AverageAnnualReturnSinceInception

0.42%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Absolute Return Credit Fund | Bank of America (BofA) Merrill Lynch U.S. Dollar 3-Month LIBOR Index (reflects no deduction for fees, expenses or taxes)

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

0.51%

rr_AverageAnnualReturnSinceInception

0.41%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

[1]

Other Expenses for Class Z shares are based on estimated amounts for the current fiscal year.

[2]

The fund's investment adviser has contractually agreed to limit ordinary operating expenses (ordinary operating expenses means all fund expenses other than extraordinary expenses, such as litigation, taxes and brokerage commissions) to the extent required to reduce fund expenses to 1.20%, 2.10% and 0.85% of the average daily net assets attributable to Class A, Class C and Class Y shares, respectively. These expense limitations are in effect through August 1, 2014. There can be no assurance that the adviser will extend the expense limitations beyond such time. While in effect, the arrangement may be terminated for a class only by agreement of the adviser and the Board of Trustees.

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Label

Element

Value

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PIONEER SERIES TRUST X

Prospectus Date

rr_ProspectusDate

Apr. 01, 2013

Pioneer Multi-Asset Ultrashort Income Fund

Objective, Primary [Text Block]

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

PIONEER MULTI-ASSET ULTRASHORT INCOME FUND

Objective [Heading]

rr_ObjectiveHeading

INVESTMENT OBJECTIVES

rr_ObjectivePrimaryTextBlock

A high level of current income.

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

Capital appreciation is a secondary objective.

Expense [Heading]

rr_ExpenseHeading

FEES AND EXPENSES OF THE FUND

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table 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 or your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Pioneer funds. More information about these and other discounts is available from your investment professional and in the "Sales charges" section of the prospectus beginning on page 48 and the "Sales charges" section of the statement of additional information beginning on page 63.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

SHAREOWNER 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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

August 1, 2014

Portfolio Turnover [Heading]

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PORTFOLIO TURNOVER

Portfolio Turnover [Text Block]

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Portfolio Turnover, Rate

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51.00%

Expense Breakpoint Discounts [Text]

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You may qualify for sales charge discounts if you or your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Pioneer funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

Other Expenses, New Fund, Based on Estimates [Text]

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Other Expenses for Class K and Class Z shares are based on estimated amounts for the current fiscal year.

Expense Example [Heading]

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EXAMPLE

Expense Example Narrative [Text Block]

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Expense Example by, Year, Caption [Text]

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IF YOU REDEEM YOUR SHARES
NUMBER OF YEARS YOU OWN YOUR SHARES

Expense Example, No Redemption, By Year, Caption [Text]

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IF YOU DO NOT REDEEM YOUR SHARES
NUMBER OF YEARS YOU OWN YOUR SHARES

Strategy [Heading]

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PRINCIPAL INVESTMENT STRATEGIES

Strategy Narrative [Text Block]

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Normally, the fund invests at least 80% of its net assets (plus the amount of borrowings, if any, for investment purposes) in floating rate instruments of U.S. and non-U.S. issuers, including: senior secured loans ("senior loans") and second lien or other subordinated or unsecured loans; debt issued by banks and other corporate, governmental and non-governmental entities; corporate bonds; mortgage-backed and asset-backed securities; event-linked bonds (also known as "catastrophe bonds"); and preferred stock. The fund also considers as floating rate instruments, and the fund may invest without limit in, adjustable rate securities, fixed rate securities with durations of less than or equal to one year, funds that invest primarily in floating rate instruments, and fixed rate securities with respect to which the fund has entered into derivative instruments to effectively convert the fixed rate interest payments into floating rate interest payments. The fund considers these investments as economic equivalents of floating rate instruments. The fund also may invest in other derivative instruments that are related to floating rate instruments or have economic characteristics similar to floating rate instruments for purposes of satisfying the 80% requirement.

Under normal circumstances, the fund's average portfolio duration will be less than two years. Duration seeks to measure the price sensitivity of a fixed income security to changes in interest rates. If the fund's average portfolio duration exceeds two years, the fund will take action to bring it within its expected range within a reasonable period of time. The assumptions that are made about a security's features and options when calculating duration may prove to be incorrect. Duration is not an exact measurement and may not reliably predict a security's price sensitivity to changes in yield or interest rates.

The fund does not have a targeted maturity range for its portfolio. The fund may invest in securities with a broad range of maturities.

The fund may invest up to 20% of its net assets in debt securities that are rated below investment grade (debt securities rated below investment grade are commonly referred to as "junk bonds") or are unrated but determined by the fund's investment adviser to be of equivalent credit quality, and those that are in default or in bankruptcy. The fund does not have a policy of maintaining a specific average credit quality of its portfolio.

The fund may invest up to 35% of its total assets in debt securities of non-U.S. issuers, including emerging market issuers. The fund does not currently intend to invest more than 25% of its total assets in any one non-U.S. country.

In addition to its investments in floating rate instruments, the fund also may invest in other securities, including debt of U.S. and non-U.S. governmental, corporate and other non-governmental issuers; mortgage-backed and asset-backed securities; convertible securities; bonds not paying current income; bonds that do not make regular interest payments; zero coupon securities; money market instruments; and other short-term investments, including cash and cash equivalents, certificates of deposit, repurchase agreements maturing in one week or less and bankers' acceptances. The fund may receive debt securities or equity securities as a result of the general restructuring of the debt of an issuer, the restructuring of a floating rate loan, or as part of a package of securities acquired with a loan.

The fund may, but is not required to, use derivatives, such as credit default swaps. The fund may use derivatives for a variety of purposes, including: as a hedge against adverse changes in the market price of securities, interest rates or currency exchange rates; as a substitute for purchasing or selling securities; and to increase the fund's return as a non-hedging strategy that may be considered speculative. The fund may invest without limit in derivative instruments. However, the fund may choose not to make use of derivatives for a variety of reasons, and any use may be limited by applicable law and regulations. The fund may hold cash or other short-term investments.

The fund's investments may have fixed or variable principal payments and all types of interest rate and dividend payment and reset terms, including fixed rate, adjustable rate, floating rate, contingent, deferred, payment in kind and auction rate features. The fund's investments may include instruments that allow for balloon payments or negative amortization payments.

The fund may invest in equity securities, including common stocks, rights, warrants, depositary receipts, exchange-traded funds (ETFs) that invest primarily in equity securities and equity interests in real estate investment trusts (REITs). The fund may invest in equity securities as a consequence of holding debt of the same issuer, when the adviser believes they offer the potential for capital gains or for other portfolio management purposes, although equity securities may not pay dividends or contribute to achieving the fund's investment objective of a high level of current income.

The adviser considers both broad economic and issuer specific factors in selecting a portfolio designed to achieve the fund's investment objectives. In assessing the appropriate duration, rating, sector and country weightings of the fund's portfolio, the adviser considers a variety of factors that are expected to influence economic activity and interest rates. These factors include fundamental economic indicators, such as the rates of economic growth and inflation, Federal Reserve monetary policy, and the relative value of the U.S. dollar compared to other currencies. Once the adviser determines the preferable portfolio characteristics, the adviser selects individual securities based upon the terms of the securities (such as yields compared to U.S. Treasuries or comparable issues), liquidity, credit quality, and sector and issuer diversification. The adviser also employs fundamental quantitative and qualitative research to assess an issuer's credit quality, taking into account financial condition and profitability, future capital needs, potential for change in rating, industry outlook, the competitive environment and management capabilities. The adviser may sell a portfolio security when it believes the security no longer will contribute to meeting the fund's investment objectives. The adviser makes that determination based on the same criteria it uses to select portfolio securities.

Risk [Heading]

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PRINCIPAL RISKS OF INVESTING IN THE FUND

Risk Narrative [Text Block]

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You could lose money on your investment in the fund. As with any mutual fund, there is no guarantee that the fund will achieve its objectives.

MARKET RISK. The values of securities held by the fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, inflation, changes in interest or currency rates or adverse investor sentiment. Adverse market conditions may be prolonged and may not have the same impact on all types of securities. The values of securities may fall due to factors affecting a particular issuer, industry or the securities market as a whole. The stock market may perform poorly relative to other investments. (This risk may be greater in the short term.) High public debt in the U.S. and other countries creates ongoing systemic and market risks and policymaking uncertainty. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. Some governmental and non-governmental issuers (notably in Europe) have defaulted on, or been forced to restructure, their debts, and many other issuers have faced difficulties obtaining credit. These market conditions may continue, worsen or spread, including in the U.S., Europe and beyond. Further defaults or restructurings by governments and others of their debt could have additional adverse effects on economies, financial markets and asset valuations around the world. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. Whether or not the fund invests in securities of issuers located in or with significant exposure to countries experiencing economic and financial difficulties, the value and liquidity of the fund's investments may be negatively affected by the countries experiencing these difficulties. In addition, policy and legislative changes in the U.S. and in other countries are affecting many aspects of financial regulation. The impact of these changes, and the practical implications for market participants, may not be fully known for some time. The fund may experience a substantial or complete loss on any individual security.

INTEREST RATE RISK. Interest rates may go up, causing the value of the fund's investments to decline (this risk generally will be greater for securities with longer maturities or durations). The fund's average portfolio maturity may be greater than the fund's average portfolio duration, and, accordingly, the fund may be more sensitive to changes in interest rates.

The values of securities with floating interest rates generally are less sensitive to interest rate changes but may decline in value if their interest rates do not rise as much, or as quickly, as prevailing interest rates. Unlike fixed rate securities, floating rate securities generally will not increase in value if interest rates decline. Changes in interest rates also will affect the amount of interest income the fund earns on its floating rate investments. Unlike fixed rate securities, when prevailing interest rates decrease, the interest rate payable on floating rate investments will decrease.

CREDIT RISK. If an issuer or guarantor of a security held by the fund or a counterparty to a financial contract with the fund defaults on its obligation to pay principal and/or interest, has its credit rating downgraded or is perceived to be less creditworthy, or the credit quality or value of any underlying assets declines, the value of your investment will decline. A security may change in price for a variety of reasons. For example, floating rate securities may have final maturities of ten or more years, but their effective durations will tend to be very short. If there is an adverse credit event, or a perceived change in the issuer's creditworthiness, these securities could experience greater negative price movement than would be predicted by the change in prevailing interest rates in relation to their effective duration. In addition, the fund may incur expenses to protect the fund's interest in securities experiencing these events. Credit risk is broadly gauged by the credit ratings of the securities in which the fund invests. However, ratings are only the opinions of the companies issuing them and are not guarantees as to quality. Junk bonds have a higher risk of default or are already in default and are considered speculative.

PREPAYMENT OR CALL RISK. Many issuers have a right to prepay their securities. If interest rates fall, an issuer may exercise this right. If this happens, the fund will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on the prepaid security. The fund also may lose any premium it paid on the security.

LIQUIDITY RISK. Some securities held by the fund may be difficult to sell, or illiquid, particularly during times of market turmoil. Illiquid securities also may be difficult to value. If the fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, the fund may be forced to sell at a loss.

EXTENSION RISK. During periods of rising interest rates, the average life of certain types of securities may be extended because of slower than expected principal payments. This may lock in a below market interest rate, increase the security's duration (the estimated period until the security is paid in full) and reduce the value of the security.

HIGH YIELD OR "JUNK" BOND RISK. Debt securities that are below investment grade, called "junk bonds," are speculative, have a higher risk of default or are already in default, tend to be less liquid and are more difficult to value than higher grade securities. Junk bonds tend to be volatile and more susceptible to adverse events and negative sentiments.

RISKS OF INVESTING IN FLOATING RATE LOANS. Floating rate loans and similar investments may be illiquid or less liquid than other investments. The value of collateral, if any, securing a floating rate loan can decline or may be insufficient to meet the issuer's obligations or may be difficult to liquidate. No active trading market may exist for many floating rate loans, and many loans are subject to restrictions on resale. Market quotations for these securities may be volatile and/or subject to large spreads between bid and ask prices. Any secondary market may be subject to irregular trading activity and extended trade settlement periods.

An intermediate participant between the fund and the borrower in a loan participation may fail to meet its obligations to the fund to enforce any rights against the borrower. In addition, the issuer of the loan may default on its obligations.

Although the features of senior loans, including being secured by collateral and having priority over other obligations of the issuer, reduce some of the risks of investment in below investment grade securities, the loans are subject to significant risks.

Certain floating rate loans and other corporate debt securities involve refinancings, recapitalizations, mergers and acquisitions, and other financings for general corporate purposes. Other loans are incurred in restructuring or "work-out" scenarios, including debtor-in-possession facilities in bankruptcy. Loans to highly leveraged companies are especially vulnerable to adverse economic or market conditions and the risk of default.

RISK OF INSUFFICIENT COLLATERAL. The value of collateral, if any, securing a floating rate loan can decline, and may be insufficient to meet the issuer's obligations or may be difficult to liquidate. In addition, the fund's access to collateral may be limited by bankruptcy or other insolvency laws.

RISK OF DISADVANTAGED ACCESS TO CONFIDENTIAL INFORMATION. The adviser's decision not to receive material, non-public information about an issuer of a loan either held by, or considered for investment by, the fund, under normal circumstances could place it at a disadvantage, relative to other loan investors, in assessing a loan or the loan's issuer, and adversely affect the fund's investment performance.

RISKS OF SUBORDINATED SECURITIES. A holder of securities that are subordinated or "junior" to more senior securities of an issuer is entitled to payment after holders of more senior securities of the issuer. Subordinated securities are more likely to suffer a credit loss than non-subordinated securities of the same issuer, any loss incurred by the subordinated securities is likely to be proportionately greater, and any recovery of interest or principal may take more time. As a result, even a perceived decline in creditworthiness of the issuer is likely to have a greater impact on them.

RISKS OF NON-U.S. INVESTMENTS. Investing in non-U.S. issuers or issuers with significant exposure to foreign markets may involve unique risks compared to investing in securities of U.S. issuers. These risks are more pronounced for issuers in emerging markets or to the extent that the fund invests significantly in one region or country. These risks may include different financial reporting practices and regulatory standards, less liquid trading markets, extreme price volatility, currency risks, changes in economic, political, regulatory and social conditions, sustained economic downturns, financial instability, tax burdens, and investment and repatriation restrictions. Lack of information and less market regulation also may affect the value of these securities. Withholding and other non-U.S. taxes may decrease the fund's return. Non-U.S. issuers may be located in parts of the world that have historically been prone to natural disasters.

U.S. GOVERNMENT AGENCY OBLIGATIONS RISK. The fund invests in obligations issued by agencies and instrumentalities of the U.S. government. Government-sponsored entities such as Federal National Mortgage Association (Fannie Mae), Federal Home Loan Mortgage Corporation (Freddie Mac) and the Federal Home Loan Banks (FHLBs), although chartered or sponsored by Congress, are not funded by congressional appropriations and the debt and mortgage-backed securities issued by them are neither guaranteed nor issued by the U.S. government. Such debt and mortgage-backed securities are subject to the risk of default on the payment of interest and/or principal, similar to debt of private issuers. Although the U.S. government has provided financial support to Fannie Mae and Freddie Mac in the past, there can be no assurance that it will support these or other government-sponsored entities in the future.

MORTGAGE-RELATED AND ASSET-BACKED SECURITIES RISK. The value of mortgage-related and asset-backed securities will be influenced by factors affecting the housing market and the assets underlying such securities. As a result, during periods of declining asset value, difficult or frozen credit markets, swings in interest rates, or deteriorating economic conditions, mortgage-related and asset-backed securities may decline in value, face valuation difficulties, become more volatile and/or become illiquid. Additionally, during such periods and also under normal conditions, these securities are also subject to prepayment and call risk. Some of these securities may receive little or no collateral protection from the underlying assets and are thus subject to the risk of default. The risk of such defaults is generally higher in the case of mortgage-backed investments that include so-called "sub-prime" mortgages. The structure of some of these securities may be complex and there may be less available information than for other types of debt securities. Upon the occurrence of certain triggering events or defaults, the fund may become the holder of underlying assets at a time when those assets may be difficult to sell or may be sold only at a loss.

RISKS OF INVESTING IN EVENT-LINKED BONDS. The return of principal and the payment of interest on "event-linked" bonds are contingent on the non-occurrence of a pre-defined "trigger" event, such as a hurricane or an earthquake of a specific magnitude. If a trigger event, as defined within the terms of an event-linked bond, involves losses or other metrics exceeding a specific magnitude in the geographic region and time period specified therein, the fund may lose a portion or all of its accrued interest and/or principal invested in such event-linked bond. In addition to the specified trigger events, event-linked bonds may expose the fund to other risks, including but not limited to issuer (credit) default, adverse regulatory or jurisdictional interpretations and adverse tax consequences.

RISKS OF INVERSE FLOATING RATE OBLIGATIONS. The interest rate on inverse floating rate obligations will generally decrease as short-term interest rates increase, and increase as short-term rates decrease. Due to their leveraged structure, the sensitivity of the market value of an inverse floating rate obligation to changes in interest rates is generally greater than a comparable long-term bond issued by the same issuer and with similar credit quality, redemption and maturity provisions. Inverse floating rate obligations may be volatile and involve leverage risk.

RISK OF INVESTMENT IN OTHER FUNDS. Investing in other investment companies subjects the fund to the risks of investing in the underlying securities or assets held by those funds. When investing in another fund, the fund will bear a pro rata portion of the underlying fund's expenses, in addition to its own expenses.

DERIVATIVES RISK. Using derivatives can increase fund losses and reduce opportunities for gains when market prices, interest rates or the derivative instruments themselves behave in a way not anticipated by the fund. Using derivatives may increase the volatility of the fund's net asset value and may not provide the result intended. Derivatives may have a leveraging effect on the fund. Some derivatives have the potential for unlimited loss, regardless of the size of the fund's initial investment. Changes in a derivative's value may not correlate well with the referenced asset or metric. The fund also may have to sell assets at inopportune times to satisfy its obligations. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the fund. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation is not yet fully known and may not be for some time. New regulation of derivatives may make them more costly, may limit their availability, or may otherwise adversely affect their value or performance.

CREDIT DEFAULT SWAP RISK. Credit default swap contracts, a type of derivative instrument, involve special risks and may result in losses to the fund. Credit default swaps may in some cases be illiquid, and they increase credit risk since the fund has exposure to both the issuer of the referenced obligation and the counterparty to the credit default swap. Swaps may be difficult to unwind or terminate. The swap market could be disrupted or limited as a result of recent legislation, and these changes could adversely affect the fund.

LEVERAGING RISK. The value of your investment may be more volatile and other risks tend to be compounded if the fund borrows or uses derivatives or other investments, such as ETFs, that have embedded leverage. Leverage generally magnifies the effect of any increase or decrease in the value of the fund's underlying assets or creates investment risk with respect to a larger pool of assets than the fund would otherwise have, potentially resulting in the loss of all assets. Engaging in such transactions may cause the fund to liquidate positions when it may not be advantageous to do so to satisfy its obligations or meet segregation requirements.

EQUITY SECURITIES RISK. Equity securities represent an ownership interest in an issuer, rank junior in a company's capital structure to debt securities and consequently may entail greater risk of loss than debt securities. Equity securities are subject to the risk that stock prices may rise and fall in periodic cycles and may perform poorly relative to other investments. This risk may be greater in the short term.

RISKS OF ZERO COUPON BONDS AND PAYMENT IN KIND SECURITIES. Zero coupon bonds and payment in kind securities may be more speculative and may fluctuate more in value than securities which pay income periodically and in cash. In addition, although the fund receives no periodic cash payments on such securities, the fund is deemed for tax purposes to receive income from such securities, which applicable tax rules require the fund to distribute to shareholders. Such distributions may be taxable when distributed to shareholders.

PORTFOLIO SELECTION RISK. The adviser's judgment about the quality, relative yield, relative value or market trends affecting a particular sector or region, market segment, security or about interest rates generally may prove to be incorrect.

MARKET SEGMENT RISK. To the extent the fund emphasizes, from time to time, investments in a market segment, the fund will be subject to a greater degree to the risks particular to that segment, and may experience greater market fluctuation than a fund without the same focus.

NOT A MONEY MARKET FUND. The fund is not a money market fund and is not subject to the strict rules that govern the quality, maturity, liquidity and other features of securities that money market funds may purchase. Under normal conditions, the fund's investments may be more susceptible than a money market fund to interest rate risk, valuation risk, credit risk and other risks relevant to the fund's investments. The fund does not attempt to maintain a stable net asset value. Therefore, the fund's net asset value per share will fluctuate.

EXPENSE RISK. Your actual costs of investing in the fund may be higher than the expenses shown in "Annual fund operating expenses" for a variety of reasons. For example, expense ratios may be higher than those shown if overall net assets decrease. Net assets are more likely to decrease and fund expense ratios are more likely to increase when markets are volatile.

Please note that there are many other factors that could adversely affect your investment and that could prevent the fund from achieving its goals.

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Lose Money [Text]

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You could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

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An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

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THE FUND'S PAST PERFORMANCE

Performance Narrative [Text Block]

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Performance Information Illustrates Variability of Returns [Text]

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Performance One Year or Less [Text]

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No performance information is presented for Class K or Class Z shares in the table because Class K and Class Z shares do not have annual returns for at least one calendar year.

Performance Availability Phone [Text]

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1-800-225-6292

Performance Availability Website Address [Text]

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https://us.pioneerinvestments.com/performance

Performance Past Does Not Indicate Future [Text]

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The fund's past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

Bar Chart [Heading]

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ANNUAL RETURN CLASS A SHARES (%)
(Year ended December 31)

Bar Chart Does Not Reflect Sales Loads [Text]

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The bar chart does not reflect any sales charge you may pay when you buy fund shares. If this amount was reflected, returns would be less than those shown.

Bar Chart Closing [Text Block]

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For the period covered by the bar chart:
THE HIGHEST CALENDAR QUARTERLY RETURN WAS 1.07% (07/01/2012 TO 09/30/2012).
THE LOWEST CALENDAR QUARTERLY RETURN WAS 0.35% (10/01/2012 TO 12/31/2012).

Performance Table Heading

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AVERAGE ANNUAL TOTAL RETURN (%)
(for periods ended December 31, 2012)

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on the investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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After-tax returns are shown only for Class A shares. After-tax returns for Class C and Class Y shares will vary.

Performance Table Narrative

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Performance Table Closing [Text Block]

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No performance information is presented for Class K or Class Z shares in the table because Class K and Class Z shares do not have annual returns for at least one calendar year. The returns for Class K and Class Z shares would differ from those of Class A, Class C and Class Y shares because they have different expenses.

Pioneer Multi-Asset Ultrashort Income Fund | CLASS A

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.35%

rr_DistributionAndService12b1FeesOverAssets

0.20%

rr_OtherExpensesOverAssets

0.48%

^[1]

rr_ExpensesOverAssets

1.03%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

^[2]

Highest Quarterly Return, Label

rr_NetExpensesOverAssets

0.85%

^[2]

rr_ExpenseExampleYear01

335

rr_ExpenseExampleYear03

552

rr_ExpenseExampleYear05

787

rr_ExpenseExampleYear10

1,462

rr_ExpenseExampleNoRedemptionYear01

335

rr_ExpenseExampleNoRedemptionYear03

552

rr_ExpenseExampleNoRedemptionYear05

787

rr_ExpenseExampleNoRedemptionYear10

1,462

2012

rr_AnnualReturn2012

2.89%

rr_HighestQuarterlyReturnLabel

HIGHEST CALENDAR QUARTERLY RETURN

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

1.07%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

LOWEST CALENDAR QUARTERLY RETURN

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.35%

rr_AverageAnnualReturnYear01

0.27%

rr_AverageAnnualReturnSinceInception

0.43%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Multi-Asset Ultrashort Income Fund | CLASS C

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.35%

rr_DistributionAndService12b1FeesOverAssets

0.50%

rr_OtherExpensesOverAssets

0.52%

^[1]

rr_ExpensesOverAssets

1.37%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

(0.22%)

^[2]

rr_NetExpensesOverAssets

1.15%

^[2]

rr_ExpenseExampleYear01

117

rr_ExpenseExampleYear03

412

rr_ExpenseExampleYear05

729

rr_ExpenseExampleYear10

1,627

rr_ExpenseExampleNoRedemptionYear01

117

rr_ExpenseExampleNoRedemptionYear03

412

rr_ExpenseExampleNoRedemptionYear05

729

rr_ExpenseExampleNoRedemptionYear10

1,627

rr_AverageAnnualReturnYear01

2.21%

rr_AverageAnnualReturnSinceInception

1.31%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Multi-Asset Ultrashort Income Fund | CLASS K

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.35%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.08%

^[1]

rr_ExpensesOverAssets

0.43%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

rr_NetExpensesOverAssets

0.43%

^[2]

rr_ExpenseExampleYear01

rr_ExpenseExampleYear03

138

rr_ExpenseExampleYear05

241

rr_ExpenseExampleYear10

542

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

138

rr_ExpenseExampleNoRedemptionYear05

241

rr_ExpenseExampleNoRedemptionYear10

542

Pioneer Multi-Asset Ultrashort Income Fund | CLASS Y

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.35%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.45%

^[1]

rr_ExpensesOverAssets

0.80%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[2]

rr_NetExpensesOverAssets

0.65%

^[2]

rr_ExpenseExampleYear01

rr_ExpenseExampleYear03

240

rr_ExpenseExampleYear05

429

rr_ExpenseExampleYear10

976

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

240

rr_ExpenseExampleNoRedemptionYear05

429

rr_ExpenseExampleNoRedemptionYear10

976

rr_AverageAnnualReturnYear01

3.10%

rr_AverageAnnualReturnSinceInception

2.26%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Multi-Asset Ultrashort Income Fund | CLASS Z

Maximum sales charge (load) when you buy shares (as a percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

rr_ManagementFeesOverAssets

0.35%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.20%

^[1]

rr_ExpensesOverAssets

0.55%

^[2]

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

rr_NetExpensesOverAssets

0.55%

^[2]

rr_ExpenseExampleYear01

rr_ExpenseExampleYear03

176

rr_ExpenseExampleYear05

307

rr_ExpenseExampleYear10

689

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

176

rr_ExpenseExampleNoRedemptionYear05

307

rr_ExpenseExampleNoRedemptionYear10

689

Pioneer Multi-Asset Ultrashort Income Fund | Return after taxes on distributions | CLASS A

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

(0.31%)

rr_AverageAnnualReturnSinceInception

(0.09%)

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Multi-Asset Ultrashort Income Fund | Return after taxes on distributions and sale of shares | CLASS A

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

0.17%

rr_AverageAnnualReturnSinceInception

0.06%

rr_AverageAnnualReturnInceptionDate

May 02, 2011

Pioneer Multi-Asset Ultrashort Income Fund | Bank of America (BofA) Merrill Lynch U.S. Dollar 3-Month LIBOR Index (reflects no deduction for fees, expenses or taxes)

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

0.51%

rr_AverageAnnualReturnSinceInception

0.41%