Risk/Return Detail Data - FidelitySeriesEmergingMarketsDebtFunds-ComboPRO	Mar. 01, 2024 USD ($)
Risk/Return:
Registrant Name	Fidelity Hastings Street Trust
FidelitySeriesEmergingMarketsDebtFunds-ComboPRO | Fidelity Series Emerging Markets Debt Local Currency Fund
Risk/Return:
Risk/Return [Heading]	Fund Summary Fund: Fidelity® Series Emerging Markets Debt Local Currency Fund
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	Fidelity® Series Emerging Markets Debt Local Currency Fund seeks high total return.
Expense [Heading]	Fee Table
Expense Narrative [Text Block]	The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund.
Shareholder Fees Caption [Text]	Shareholder fees
(fees paid directly from your investment)	none
Operating Expenses Caption [Text]	Annual Operating Expenses
Fee Waiver or Reimbursement over Assets, Date of Termination	April 30, 2027
Portfolio Turnover [Heading]	Portfolio Turnover
Portfolio Turnover [Text Block]	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 71% of the average value of its portfolio.
Portfolio Turnover, Rate	71.00%
Expense Example Narrative [Text Block]	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 the 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:
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	Normally investing at least 80% of assets in debt securities of issuers in emerging markets and other debt investments that are tied economically to emerging markets and denominated in the local currency of the issuer. Emerging markets include countries that have an emerging stock market as defined by MSCI, countries or markets with low- to middle-income economies as classified by currency of the World Bank, and other countries or markets with similar emerging characteristics. Emerging markets tend to have relatively low gross national product per capita compared to the world's major economies and may have the potential for rapid economic growth.Investing up to 20% of the fund's net assets in securities that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - to adjust the fund's risk exposure - as well as forward foreign currency exchange contracts for both hedging and non-hedging purposes.Potentially investing in other types of securities, including debt securities of non-emerging markets foreign issuers and lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds) of U.S. issuers.Allocating investments across different emerging markets countries.Actively managing the fund's currency exposures. Utilizing forward foreign currency exchange contracts for both hedging and non-hedging purposes.Analyzing a security's structural features and current pricing, trading opportunities, and the credit, currency, and economic risks of the security and its issuer to select investments.
Risk [Heading]	Principal Investment Risks
Risk Narrative [Text Block]	Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease. Foreign and Emerging Markets Risk. Foreign markets, particularly emerging 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. The extent of economic development; political stability; market depth, infrastructure, and capitalization; and regulatory oversight can be less than in more developed markets. Emerging markets typically have less established legal, accounting and financial reporting systems than those in more developed markets, which may reduce the scope or quality of financial information available to investors. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile. Geographic Exposure to Europe. Because the fund invests a meaningful portion of its assets in Europe, the fund's performance is expected to be closely tied to social, political, and economic conditions within Europe and to be more volatile than the performance of more geographically diversified funds. Geographic Exposure to Latin America. Because the fund invests a meaningful portion of its assets in Latin America, the fund's performance is expected to be closely tied to social, political, and economic conditions within Latin America and to be more volatile than the performance of more geographically diversified funds. Foreign Currency Transactions. The fund may enter into forward foreign currency exchange contracts for both hedging and non-hedging purposes. A forward foreign currency exchange contract, which involves an obligation to purchase or sell a specific currency at a future date at a price set at the time of the contract, reduces a fund's exposure to changes in the value of the currency it will deliver and increases its exposure to changes in the value of the currency it will receive for the duration of the contract. Foreign exchange rates can be extremely volatile and the degree of volatility of the market or in the direction of the market from that anticipated by the Adviser may result in losses to the fund. Currency Exposure. Because the fund is normally heavily exposed to foreign currencies, it could experience losses based solely on the weakness of foreign currencies versus the U.S. dollar and changes in the exchange rates between foreign currencies and the U.S. dollar. Currency risk may be particularly high to the extent that a fund invests in foreign currencies or engages in foreign currency transactions that are economically tied to emerging markets countries. These emerging markets currency transactions may present market, credit, currency, liquidity, legal, political and other risks different from, or greater than, the risks of investing in developed foreign currencies or engaging in foreign currency transactions that are economically tied to developed foreign countries. 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. Lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell. Leverage Risk. Derivatives, forward-settling securities and short sale transactions involve leverage because they can provide investment exposure in an amount exceeding the initial investment. Leverage can magnify investment risks and cause losses to be realized more quickly. A small change in the underlying asset, instrument, or index can lead to a significant loss. Forward-settling securities and short sale transactions also involve the risk that a security will not be issued, delivered, available for purchase, or paid for when anticipated. An increase in the market price of securities sold short will result in a loss. Government legislation or regulation could affect the use of these transactions and could limit a fund's ability to pursue its investment strategies. In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), 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]	You could lose money by investing in the fund.
Risk Nondiversified Status [Text]	In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), 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.
Risk Not Insured Depository Institution [Text]	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.
Bar Chart and Performance Table [Heading]	Performance
Performance Narrative [Text Block]	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 over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]	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 over various periods of time.
Performance Availability Website Address [Text]	www.fidelity.com
Performance Past Does Not Indicate Future [Text]	Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]	Year-by-Year Returns
Annual Return, Inception Date	Oct. 30, 2020
Highest Quarterly Return, Label	Highest Quarter Return
Highest Quarterly Return, Date	Dec. 31, 2022
Highest Quarterly Return	9.03%
Lowest Quarterly Return, Label	Lowest Quarter Return
Lowest Quarterly Return, Date	Jun. 30, 2022
Lowest Quarterly Return	(7.88%)
Performance Table Heading	Average Annual Returns
Performance Table Uses Highest Federal Rate	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	The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher	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.
Performance Table Narrative	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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelitySeriesEmergingMarketsDebtFunds-ComboPRO | Fidelity Series Emerging Markets Debt Local Currency Fund | Fidelity Series Emerging Markets Debt Local Currency Fund
Risk/Return:
Management fee	none
Distribution and/or Service (12b-1) fees	none
Other expenses	0.02%
Total annual operating expenses	0.02%
Fee waiver and/or expense reimbursement	0.02%	[1]
Total annual operating expenses after fee waiver and/or expense reimbursement	none
1 year	none
3 years	none
5 years	4
10 years	$ 19
2021	(8.56%)
2022	(7.85%)
2023	13.53%
FidelitySeriesEmergingMarketsDebtFunds-ComboPRO | Fidelity Series Emerging Markets Debt Local Currency Fund | Return Before Taxes | Fidelity Series Emerging Markets Debt Local Currency Fund
Risk/Return:
Label	Return Before Taxes
Past 1 year	13.53%
Since Inception	1.25%	[2]
FidelitySeriesEmergingMarketsDebtFunds-ComboPRO | Fidelity Series Emerging Markets Debt Local Currency Fund | After Taxes on Distributions | Fidelity Series Emerging Markets Debt Local Currency Fund
Risk/Return:
Label	Return After Taxes on Distributions
Past 1 year	11.20%
Since Inception	(0.09%)	[2]
FidelitySeriesEmergingMarketsDebtFunds-ComboPRO | Fidelity Series Emerging Markets Debt Local Currency Fund | After Taxes on Distributions and Sales | Fidelity Series Emerging Markets Debt Local Currency Fund
Risk/Return:
Label	Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year	7.97%
Since Inception	0.39%	[2]
FidelitySeriesEmergingMarketsDebtFunds-ComboPRO | Fidelity Series Emerging Markets Debt Local Currency Fund | JP084
Risk/Return:
Label	J.P. Morgan GBI-EM Global Diversified Index
Past 1 year	12.70%
Since Inception	(0.27%)	[2]

[1] AFidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, fees and expenses of the Independent Trustees, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.003% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through April 30, 2027. FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.

[2] AFrom October 30, 2020.