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Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName FIDELITY OXFORD STREET TRUST
Prospectus Date rr_ProspectusDate Sep. 29, 2018
07.31 Fidelity Commodity Strategy Fund F PRO-03 | Fidelity® Commodity Strategy Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading <p style="font: bold 20pt Arial, Helvetica, sans-serif;">Fund Summary</p><p style="font: normal 12pt Arial, Helvetica, sans-serif;"><b>Fund/Class</b>:<br/><b>Fidelity® Commodity Strategy Fund</b>/F</p>
Objective [Heading] rr_ObjectiveHeading <font style="font: bold 16pt Arial, Helvetica, sans-serif;">Investment Objective</font>
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund seeks to provide investment returns that correspond to the performance of the commodities market.
Expense [Heading] rr_ExpenseHeading <font style="font: bold 16pt Arial, Helvetica, sans-serif;"><b>Fee Table</b></font>
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 Caption [Text] rr_ShareholderFeesCaption <p style="font: bold 11pt Arial, sans-serif; margin-bottom: 0px;">Shareholder fees</p><p style="font: bold 9pt Arial, sans-serif; margin-top: 0px"></p>
(fees paid directly from your investment) rr_ShareholderFeeOther none
Operating Expenses Caption [Text] rr_OperatingExpensesCaption <p style="font: bold 11pt Arial, sans-serif; margin-bottom: 0px;">Annual Operating Expenses</p><p style="font: bold 9pt Arial, sans-serif; margin-top: 0px">(expenses that you pay each year as a % of the value of your investment)</p>
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading <font style="font: bold 16pt Arial, Helvetica, sans-serif;"><b>Portfolio Turnover</b></font>
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 0% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate none
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 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:

Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption <p style="font: bold 9pt Arial, sans-serif; margin-top: 0px">Sell All Shares</p>
Strategy [Heading] rr_StrategyHeading <font style="font: bold 16pt Arial, Helvetica, sans-serif;"><b>Principal Investment Strategies</b></font>
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing in commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
  • Investing up to 25% of assets in a wholly-owned subsidiary organized under the laws of the Cayman Islands that invests in commodity-linked total return swaps based on the value of commodities or commodities indexes and in other commodity-linked derivative instruments.
  • Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2018 was the Bloomberg Commodity Index Total Return℠.
  • Investing in domestic and foreign issuers.
  • Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
  • Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity® funds to invest in particular security types or investment disciplines).
Risk [Heading] rr_RiskHeading <font style="font: bold 16pt Arial, Helvetica, sans-serif;"><b>Principal Investment Risks</b></font>
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • 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.
  • Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
  • Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
  • 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.
  • Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
  • Commodity-Linked Investing. The value of commodities and commodity-linked investments may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures.
  • Commodity Futures. Investments in commodity futures contracts are also subject to the risk of the failure of any of the exchanges on which the fund’s positions trade or of its clearinghouses or counterparties. In addition, certain commodity exchanges limit fluctuations in certain futures contract prices during a single day by regulations referred to as "daily price fluctuation limits" or "daily limits." Under such daily limits, during a single trading day no trades may be executed at prices beyond the daily limit. If triggered, these limits could prevent the fund from liquidating unfavorable positions and subject the fund to losses or prevent it from entering into desired trades during the particular trading day.

In addition, the fund is classified as non-diversified under the Investment Company Act of 1940, which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 Lose Money [Text] rr_RiskLoseMoney <font style="FONT-FAMILY: Times New Roman" size="3">You could lose money by investing in the fund.</font>
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus <font style="FONT-FAMILY: Times New Roman" size="3">In addition, the fund is classified as non-diversified under the Investment Company Act of 1940, which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.</font>
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution <font style="FONT-FAMILY: Times New Roman" size="3">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.</font>
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading <font style="font: bold 16pt Arial, Helvetica, sans-serif;"><b>Performance</b></font>
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

Performance history will be available for the fund after the fund has been in operation for one calendar year.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess <font style="FONT-FAMILY: Times New Roman" size="3">Performance history will be available for the fund after the fund has been in operation for one calendar year.</font>
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress <font style="FONT-FAMILY: Times New Roman" size="3">www.fidelity.com</font>
07.31 Fidelity Commodity Strategy Fund F PRO-03 | Fidelity® Commodity Strategy Fund | Fidelity Commodity Strategy Fund-Class F Fidelity  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets none
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05% [1]
Total annual operating expenses rr_ExpensesOverAssets 0.45%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.05% [1]
Total annual operating expenses after fee waiver and/or expense reimbursement rr_NetExpensesOverAssets 0.40%
1 year rr_ExpenseExampleYear01 $ 41
3 years rr_ExpenseExampleYear03 128
5 years rr_ExpenseExampleYear05 224
10 years rr_ExpenseExampleYear10 $ 505
[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Geode Capital Management, LLC (Geode) for the management of its portfolio pursuant to which the subsidiary pays Geode a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. Geode has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to Geode by the subsidiary. This arrangement will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as Geode's contract with the subsidiary is in place. If Geode's contract with the subsidiary is terminated, Geode, in its sole discretion, may discontinue the arrangement.