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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Feb. 28, 2012
Registrant Name dei_EntityRegistrantName FIDELITY OXFORD STREET TRUST
Central Index Key dei_EntityCentralIndexKey 0000028540
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Apr. 26, 2012
Document Effective Date dei_DocumentEffectiveDate Apr. 28, 2012
Prospectus Date rr_ProspectusDate Apr. 28, 2012
Fidelity Four-in-One Index Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund:
Fidelity® Four-in-One Index Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks high total return.
Fee Table fost_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual fund operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual fund operating expenses (expenses that you pay each year as a % of the value of your investment)
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses. As a result, the total annual fund operating expenses after fee waiver and/or expense reimbursement in the fee table exceed the contractual expense limitation of the fund.
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination April 30, 2015
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This example helps compare the cost of investing in the fund with the cost of investing in other mutual funds.

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:
Portfolio Turnover fost_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The fund will not incur transaction costs, such as commissions, when it buys and sells shares of underlying Fidelity funds (or "turns over" its portfolio), but it could incur transaction costs if it were to buy and sell other types of securities directly. If the fund were to buy and sell other types of securities directly, a higher portfolio turnover rate could indicate higher transaction costs and could result in higher taxes when fund shares are held in a taxable account. Such costs, if incurred, would not be reflected in annual operating expenses or in the example and would affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 16% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 16.00%
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Investing in a combination of four Fidelity stock and bond index funds (underlying Fidelity funds) using an asset allocation strategy designed for investors seeking a broadly diversified, index-based investment.
  • Allocating assets among underlying Fidelity index funds according to a target asset allocation of approximately:
 Investment %
  Spartan® 500 Index Fund 48%
  
  Spartan® Extended Market Index Fund12%
  
  Spartan International Index Fund25%
  
  Spartan U.S. Bond Index Fund15%
  
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Investing in Other Funds. The fund bears all risks of investment strategies employed by the underlying funds, including the risk that the underlying funds will not meet their investment objectives.
  • Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market can react differently to these developments.
  • Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
  • Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
  • Prepayment. The ability of an issuer of a debt security to repay principal prior to a security’s maturity can cause greater price volatility if interest rates change.
  • Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
  • Correlation to Index. The performance of an underlying index fund and its index may vary somewhat due to factors such as transaction costs, sample selection, and timing differences associated with additions to and deletions from the index.
  • Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
  • Small Cap Investing. The value of securities of smaller, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers.

An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. You could lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney You could lose money by investing in the fund.
Performance fost_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return15.86%June 30, 2009
Lowest Quarter Return-18.44%December 31, 2008
Year-to-Date Return10.55%March 31, 2012
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement. Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.
For the periods ended
December 31, 2011
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.
Fidelity Four-in-One Index Fund | Class: Fidelity Four-in-One Index Fund
  
Shareholder fees rr_ShareholderFeesAbstract  
Annual index fund fee (for fund balances under $10,000) rr_MaximumAccountFee 10.00
Annual fund operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.10%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets none
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.13%
Total annual fund operating expenses rr_ExpensesOverAssets 0.23% [1]
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.02% [2]
Total annual operating expenses after fee waiver and/or expense reimbursement rr_NetExpensesOverAssets 0.21% [1]
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 22
3 years rr_ExpenseExampleYear03 68
5 years rr_ExpenseExampleYear05 123
10 years rr_ExpenseExampleYear10 286
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (15.97%)
2003 rr_AnnualReturn2003 28.25%
2004 rr_AnnualReturn2004 12.34%
2005 rr_AnnualReturn2005 6.47%
2006 rr_AnnualReturn2006 15.43%
2007 rr_AnnualReturn2007 6.16%
2008 rr_AnnualReturn2008 (32.62%)
2009 rr_AnnualReturn2009 25.00%
2010 rr_AnnualReturn2010 13.66%
2011 rr_AnnualReturn2011 (1.39%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.86%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (18.44%)
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 10.55%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2012
Fidelity Four-in-One Index Fund | Return Before Taxes | Class: Fidelity Four-in-One Index Fund
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Fidelity Four-in-One Index Fund
Label rr_AverageAnnualReturnLabel Return Before Taxes
Past 1 year rr_AverageAnnualReturnYear01 (1.39%)
Past 5 years rr_AverageAnnualReturnYear05 0.04%
Past 10 years rr_AverageAnnualReturnYear10 4.08%
Fidelity Four-in-One Index Fund | Return After Taxes on Distributions | Class: Fidelity Four-in-One Index Fund
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Fidelity Four-in-One Index Fund
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
Past 1 year rr_AverageAnnualReturnYear01 (1.79%)
Past 5 years rr_AverageAnnualReturnYear05 (0.46%)
Past 10 years rr_AverageAnnualReturnYear10 3.57%
Fidelity Four-in-One Index Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Four-in-One Index Fund
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Fidelity Four-in-One Index Fund
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year rr_AverageAnnualReturnYear01 (0.45%)
Past 5 years rr_AverageAnnualReturnYear05 (0.10%)
Past 10 years rr_AverageAnnualReturnYear10 3.35%
Fidelity Four-in-One Index Fund | S&P 500® Index (reflects no deduction for fees, expenses, or taxes)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500®Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Past 1 year rr_AverageAnnualReturnYear01 2.11%
Past 5 years rr_AverageAnnualReturnYear05 (0.25%)
Past 10 years rr_AverageAnnualReturnYear10 2.92%
Fidelity Four-in-One Index Fund | Fidelity Four-in-One Composite Index (reflects no deduction for fees or expenses)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Fidelity Four-in-One Composite Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees or expenses)
Past 1 year rr_AverageAnnualReturnYear01 (1.25%)
Past 5 years rr_AverageAnnualReturnYear05 0.16%
Past 10 years rr_AverageAnnualReturnYear10 4.20%
[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses. As a result, the total annual fund operating expenses after fee waiver and/or expense reimbursement in the fee table exceed the contractual expense limitation of the fund.
[2] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Fidelity Four-in-One Index Fund to the extent that total operating expenses (excluding interest, taxes, certain securities lending costs, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of its average net assets, exceed 0.08%. This arrangement will remain in effect through April 30, 2015.