485BPOS

Securities Act of 1933 Registration No. 002-11517

Investment Company Act of 1940 Registration No. 811-00215

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 x

o Pre-Effective Amendment No.  ______

x Post-Effective Amendment No.  170

and

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 x

x Amendment No.  170

Fidelity Hastings Street Trust

 (Exact Name of Registrant as Specified in Charter)

245 Summer Street, Boston, Massachusetts 02210

(Address of Principal Executive Offices)(Zip Code)

Registrant’s Telephone Number: 617-563-7000

Marc Bryant, Secretary

245 Summer Street

Boston, Massachusetts 02210

(Name and Address of Agent for Service)

It is proposed that this filing will become effective immediately upon filing pursuant to paragraph (b) of Rule 485.

EXHIBIT INDEX

Exhibit	Exhibit No.
XBRL Instance Document	EX-101.INS
XBRL Taxonomy Extension Schema Document	EX-101.SCH
XBRL Taxonomy Extension Calculation Linkbase Document	EX-101.CAL
XBRL Taxonomy Extension Definition Linkbase Document	EX-101.DEF
XBRL Taxonomy Extension Labels Linkbase Document	EX-101.LAB
XBRL Taxonomy Extension Presentation Linkbase Document	EX-101.PRE

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for the effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Post-Effective Amendment No. 170 to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston, and Commonwealth of Massachusetts, on the 14th day of September 2018.

Fidelity Hastings Street Trust

	By	/s/Stacie M. Smith
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||		Stacie M. Smith, President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

(Signature)		(Title)	(Date)
/s/Stacie M. Smith		President and Treasurer	September 14, 2018
Stacie M. Smith		(Principal Executive Officer)
/s/John J. Burke III		Chief Financial Officer	September 14, 2018
John J. Burke III		(Principal Financial Officer)
/s/James C. Curvey	*	Trustee	September 14, 2018
James C. Curvey
/s/Dennis J. Dirks	*	Trustee	September 14, 2018
Dennis J. Dirks
/s/Donald F. Donahue	*	Trustee	September 14, 2018
Donald F. Donahue
/s/Alan J. Lacy	*	Trustee	September 14, 2018
Alan J. Lacy
/s/Ned C. Lautenbach	*	Trustee	September 14, 2018
Ned C. Lautenbach
/s/Joseph Mauriello	*	Trustee	September 14, 2018
Joseph Mauriello
/s/Charles S. Morrison	*	Trustee	September 14, 2018
Charles S. Morrison
/s/Cornelia M. Small	*	Trustee	September 14, 2018
Cornelia M. Small
/s/Garnett A. Smith	*	Trustee	September 14, 2018
Garnett A. Smith
/s/David M. Thomas	*	Trustee	September 14, 2018
David M. Thomas
/s/Michael E. Wiley	*	Trustee	September 14, 2018
Michael E. Wiley

*	By:	/s/Megan C. Johnson
		Megan C. Johnson, pursuant to powers of attorney dated March 2, 2018 and filed herewith.

POWER OF ATTORNEY

We, the undersigned Directors or Trustees, as the case may be, of the following investment companies:

Fidelity Advisor Series I Fidelity Advisor Series VII Fidelity Advisor Series VIII Fidelity Beacon Street Trust Fidelity Capital Trust Fidelity Central Investment Portfolios LLC Fidelity Commonwealth Trust Fidelity Commonwealth Trust II Fidelity Concord Street Trust Fidelity Congress Street Fund Fidelity Contrafund Fidelity Covington Trust Fidelity Destiny Portfolios Fidelity Devonshire Trust Fidelity Exchange Fund Fidelity Financial Trust Fidelity Hanover Street Trust Fidelity Hastings Street Trust Fidelity Investment Trust Fidelity Magellan Fund Fidelity Mt. Vernon Street Trust Fidelity Puritan Trust Fidelity Securities Fund Fidelity Select Portfolios Fidelity Summer Street Trust Fidelity Trend Fund Variable Insurance Products Fund Variable Insurance Products Fund II Variable Insurance Products Fund III Variable Insurance Products Fund IV

in addition to any other investment company for which Fidelity Management & Research Company (“FMR”) or an affiliate acts as investment adviser and for which the undersigned individuals serve as Directors or Trustees (collectively, the “Funds”), hereby revoke all previous powers of attorney we have given to sign and otherwise act in our names and behalf in matters involving any investment company for which FMR or an affiliate acts as investment adviser and hereby constitute and appoint Thomas C. Bogle, John V. O’Hanlon, Robert W. Helm, Megan C. Johnson, and Anthony H. Zacharski, each of them singly, our true and lawful attorneys-in-fact, with full power of substitution, and with full power to each of them, to sign for us and in our names in the appropriate capacities, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post-Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in our names and behalf in connection therewith as said attorneys–in-fact deem necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission.  We hereby ratify and confirm all that said attorneys-in-fact or their substitutes may do or cause to be done by virtue hereof.  This power of attorney is effective for all documents filed on or after March 2, 2018.

WITNESS our hands on this second day of March 2018.

/s/ James C. Curvey	/s/ Joseph Mauriello
James C. Curvey	Joseph Mauriello
/s/ Dennis J. Dirks	/s/ Charles S. Morrison
Dennis J. Dirks	Charles S. Morrison
/s/ Donald F. Donahue	/s/ Cornelia M. Small
Donald F. Donahue	Cornelia M. Small
/s/ Alan J. Lacy	/s/ Garnett A. Smith
Alan J. Lacy	Garnett A. Smith
/s/ Ned C. Lautenbach	/s/ David M. Thomas
Ned C. Lautenbach	David M. Thomas

POWER OF ATTORNEY

I, the undersigned Director or Trustee, as the case may be, of the following investment companies:

Fidelity Advisor Series I Fidelity Advisor Series VII Fidelity Beacon Street Trust Fidelity Capital Trust Fidelity Central Investment Portfolios LLC Fidelity Commonwealth Trust Fidelity Commonwealth Trust II Fidelity Congress Street Fund Fidelity Contrafund Fidelity Covington Trust Fidelity Destiny Portfolios Fidelity Devonshire Trust Fidelity Exchange Fund Fidelity Financial Trust Fidelity Hanover Street Trust Fidelity Hastings Street Trust Fidelity Magellan Fund Fidelity Mt. Vernon Street Trust Fidelity Select Portfolios Fidelity Summer Street Trust Fidelity Trend Fund Variable Insurance Products Fund II Variable Insurance Products Fund III Variable Insurance Products Fund IV

in addition to any other investment company for which Fidelity Management & Research Company (“FMR”) or an affiliate acts as investment adviser and for which the undersigned individual serves as Director or Trustee (collectively, the “Funds”), hereby revokes all previous powers of attorney I have given to sign and otherwise act in my name and behalf in matters involving any investment company for which FMR or an affiliate acts as investment adviser and hereby constitute and appoint Thomas C. Bogle, John V. O’Hanlon, Robert W. Helm, Megan C. Johnson, and Anthony H. Zacharski, each of them singly, my true and lawful attorneys-in-fact, with full power of substitution, and with full power to each of them, to sign for me and in my name in the appropriate capacities, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post-Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in my name and behalf in connection therewith as said attorneys–in-fact deem necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission.  I hereby ratify and confirm all that said attorneys-in-fact or their substitutes may do or cause to be done by virtue hereof.  This power of attorney is effective for all documents filed on or after March 2, 2018.

WITNESS our hands on this second day of March 2018.

/s/ Michael E. Wiley    

Michael E. Wiley

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Jun. 30, 2018
Registrant Name	dei_EntityRegistrantName	FIDELITY HASTINGS STREET TRUST
Central Index Key	dei_EntityCentralIndexKey	0000035348
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Aug. 27, 2018
Document Effective Date	dei_DocumentEffectiveDate	Aug. 29, 2018
Prospectus Date	rr_ProspectusDate	Aug. 29, 2018

XML

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund

Fund Summary

Fund/Class:
Fidelity® Mega Cap Stock Fund/Fidelity Advisor® Mega Cap Stock Fund A, M, C, I, Z

Investment Objective

The fund seeks high total return through a combination of current income and capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund. In addition to the fees and expenses described below, your broker may also require you to pay brokerage commissions on purchases and sales of certain share classes of the fund.

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other Fidelity^® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 28 of the prospectus. Different intermediaries may provide additional waivers or reductions of the sales charge. Please see “Sales Charge Waiver Policies Applied by Certain Intermediaries” in the “Appendix” section of the prospectus.

Shareholder fees

(fees paid directly from your investment)

Shareholder Fees {- Fidelity® Mega Cap Stock Fund} - 06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 - Fidelity® Mega Cap Stock Fund	Fidelity Mega Cap Stock Fund-Class A		Fidelity Mega Cap Stock Fund-Class M		Fidelity Mega Cap Stock Fund-Class C		Fidelity Mega Cap Stock Fund- Class I	Fidelity Mega Cap Stock Fund-Class Z Equity
Maximum sales charge (load) on purchases (as a % of offering price)	5.75%		3.50%		none		none	none
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	none	[1]	none	[1]	1.00%	[2]	none	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Mega Cap Stock Fund} - 06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 - Fidelity® Mega Cap Stock Fund	Fidelity Mega Cap Stock Fund-Class A	Fidelity Mega Cap Stock Fund-Class M	Fidelity Mega Cap Stock Fund-Class C	Fidelity Mega Cap Stock Fund- Class I	Fidelity Mega Cap Stock Fund-Class Z Equity
Management fee	0.44%	0.44%	0.44%	0.44%	0.44%
Distribution and/or Service (12b-1) fees	0.25%	0.50%	1.00%	none	none
Other expenses	0.24%	0.25%	0.24%	0.23%	0.09%
Total annual operating expenses	0.93%	1.19%	1.68%	0.67%	0.53%

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 and if you hold your shares:

Sell All Shares

Expense Example {- Fidelity® Mega Cap Stock Fund} - 06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 - Fidelity® Mega Cap Stock Fund - USD ($)	Fidelity Mega Cap Stock Fund-Class A	Fidelity Mega Cap Stock Fund-Class M	Fidelity Mega Cap Stock Fund-Class C	Fidelity Mega Cap Stock Fund- Class I	Fidelity Mega Cap Stock Fund-Class Z Equity
1 year	$ 664	$ 467	$ 271	$ 68	$ 54
3 years	854	715	530	214	170
5 years	1,060	981	913	373	296
10 years	$ 1,652	$ 1,743	$ 1,987	$ 835	$ 665

Hold Shares

Expense Example, No Redemption {- Fidelity® Mega Cap Stock Fund} - 06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 - Fidelity® Mega Cap Stock Fund - USD ($)	Fidelity Mega Cap Stock Fund-Class A	Fidelity Mega Cap Stock Fund-Class M	Fidelity Mega Cap Stock Fund-Class C	Fidelity Mega Cap Stock Fund- Class I	Fidelity Mega Cap Stock Fund-Class Z Equity
1 Year	$ 664	$ 467	$ 171	$ 68	$ 54
3 Years	854	715	530	214	170
5 Years	1,060	981	913	373	296
10 Years	$ 1,652	$ 1,743	$ 1,987	$ 835	$ 665

Portfolio Turnover

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 39% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing at least 80% of assets in common stocks of companies with mega market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the Russell Top 200^® Index or the S&P 100^® Index).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

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.

Performance

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 an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit institutional.fidelity.com for more recent performance information.

The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart for Class A:	Returns	Quarter ended
Highest Quarter Return	18.23%	June 30, 2009
Lowest Quarter Return	-13.14%	September 30, 2011
Year-to-Date Return	0.41%	June 30, 2018

Average Annual Returns

Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges. 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. After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary. 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.

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity® Mega Cap Stock Fund} - 06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 - Fidelity® Mega Cap Stock Fund	Past 1 year	Past 5 years	Since Inception	[1]	Inception Date
Fidelity Mega Cap Stock Fund-Class A | Return Before Taxes	10.74%	12.76%	8.05%		Feb. 05, 2008
Fidelity Mega Cap Stock Fund-Class A | After Taxes on Distributions	6.74%	11.30%	7.25%		Feb. 05, 2008
Fidelity Mega Cap Stock Fund-Class A | After Taxes on Distributions and Sales	8.97%	10.01%	6.44%		Feb. 05, 2008
Fidelity Mega Cap Stock Fund-Class M | Return Before Taxes	13.11%	13.03%	8.03%		Feb. 05, 2008
Fidelity Mega Cap Stock Fund-Class C | Return Before Taxes	15.63%	13.28%	7.90%		Feb. 05, 2008
Fidelity Mega Cap Stock Fund- Class I | Return Before Taxes	17.77%	14.42%	9.00%		Feb. 05, 2008
Fidelity Mega Cap Stock Fund-Class Z Equity | Return Before Taxes	17.97%		11.72%		Aug. 13, 2013
S&P 500® Index(reflects no deduction for fees, expenses, or taxes)	21.83%	15.79%	9.60%
Russell Top 200® Index(reflects no deduction for fees, expenses, or taxes)	22.96%	16.01%	9.50%

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class A

Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class M

Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class C

On Class C shares redeemed less than one year after purchase.

[1] Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

[2] On Class C shares redeemed less than one year after purchase.

[1] From February 5, 2008 for Class A, Class M, Class C, and Class I; and August 13, 2013 for Class Z.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Mega Cap Stock Fund/Fidelity Advisor® Mega Cap Stock Fund A, M, C, I, Z

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks high total return through a combination of current income and capital appreciation.

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. In addition to the fees and expenses described below, your broker may also require you to pay brokerage commissions on purchases and sales of certain share classes of the fund.

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other Fidelity^® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 28 of the prospectus. Different intermediaries may provide additional waivers or reductions of the sales charge. Please see “Sales Charge Waiver Policies Applied by Certain Intermediaries” in the “Appendix” section of the prospectus.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 39% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

39.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other Fidelity® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 28 of the prospectus.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

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 and if you hold your shares:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Sell All Shares

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

rr_ExpenseExampleNoRedemptionByYearCaption

Hold Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing at least 80% of assets in common stocks of companies with mega market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the Russell Top 200^® Index or the S&P 100^® Index).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

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

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.

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 an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit institutional.fidelity.com for more recent performance 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 an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

institutional.fidelity.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Bar Chart [Heading]

rr_BarChartHeading

Year-by-Year Returns

Calendar Years

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the periods shown in the chart for Class A:	Returns	Quarter ended
Highest Quarter Return	18.23%	June 30, 2009
Lowest Quarter Return	-13.14%	September 30, 2011
Year-to-Date Return	0.41%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges.

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary.

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.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges. 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. After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary. 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.

For the periods ended December 31, 2017

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

5.75%

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

^[1]

Management fee

rr_ManagementFeesOverAssets

0.44%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual operating expenses

rr_ExpensesOverAssets

0.93%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

1 year

rr_ExpenseExampleYear01

$ 664

3 years

rr_ExpenseExampleYear03

854

5 years

rr_ExpenseExampleYear05

1,060

10 years

rr_ExpenseExampleYear10

1,652

1 Year

rr_ExpenseExampleNoRedemptionYear01

664

3 Years

rr_ExpenseExampleNoRedemptionYear03

854

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,060

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,652

2009

rr_AnnualReturn2009

28.14%

2010

rr_AnnualReturn2010

14.10%

2011

rr_AnnualReturn2011

1.97%

2012

rr_AnnualReturn2012

19.18%

2013

rr_AnnualReturn2013

32.89%

2014

rr_AnnualReturn2014

11.23%

2015

rr_AnnualReturn2015

(1.74%)

2016

rr_AnnualReturn2016

13.33%

2017

rr_AnnualReturn2017

17.49%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

0.41%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.23%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(13.14%)

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class M

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

3.50%

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

^[1]

Management fee

rr_ManagementFeesOverAssets

0.44%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other expenses

rr_OtherExpensesOverAssets

0.25%

Total annual operating expenses

rr_ExpensesOverAssets

1.19%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

1 year

rr_ExpenseExampleYear01

$ 467

3 years

rr_ExpenseExampleYear03

715

5 years

rr_ExpenseExampleYear05

981

10 years

rr_ExpenseExampleYear10

1,743

1 Year

rr_ExpenseExampleNoRedemptionYear01

467

3 Years

rr_ExpenseExampleNoRedemptionYear03

715

5 Years

rr_ExpenseExampleNoRedemptionYear05

981

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,743

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[2]

Management fee

rr_ManagementFeesOverAssets

0.44%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual operating expenses

rr_ExpensesOverAssets

1.68%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On Class C shares redeemed less than one year after purchase.

1 year

rr_ExpenseExampleYear01

$ 271

3 years

rr_ExpenseExampleYear03

530

5 years

rr_ExpenseExampleYear05

913

10 years

rr_ExpenseExampleYear10

1,987

1 Year

rr_ExpenseExampleNoRedemptionYear01

171

3 Years

rr_ExpenseExampleNoRedemptionYear03

530

5 Years

rr_ExpenseExampleNoRedemptionYear05

913

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,987

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund- Class I

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

Management fee

rr_ManagementFeesOverAssets

0.44%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.23%

Total annual operating expenses

rr_ExpensesOverAssets

0.67%

1 year

rr_ExpenseExampleYear01

$ 68

3 years

rr_ExpenseExampleYear03

214

5 years

rr_ExpenseExampleYear05

373

10 years

rr_ExpenseExampleYear10

835

1 Year

rr_ExpenseExampleNoRedemptionYear01

68

3 Years

rr_ExpenseExampleNoRedemptionYear03

214

5 Years

rr_ExpenseExampleNoRedemptionYear05

373

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 835

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Class Z Equity

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

Management fee

rr_ManagementFeesOverAssets

0.44%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.09%

Total annual operating expenses

rr_ExpensesOverAssets

0.53%

1 year

rr_ExpenseExampleYear01

$ 54

3 years

rr_ExpenseExampleYear03

170

5 years

rr_ExpenseExampleYear05

296

10 years

rr_ExpenseExampleYear10

665

1 Year

rr_ExpenseExampleNoRedemptionYear01

54

3 Years

rr_ExpenseExampleNoRedemptionYear03

170

5 Years

rr_ExpenseExampleNoRedemptionYear05

296

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 665

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Return Before Taxes | Fidelity Mega Cap Stock Fund-Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Class A - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

10.74%

Past 5 years

rr_AverageAnnualReturnYear05

12.76%

Since Inception

rr_AverageAnnualReturnSinceInception

8.05%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Return Before Taxes | Fidelity Mega Cap Stock Fund-Class M

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Class M - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

13.11%

Past 5 years

rr_AverageAnnualReturnYear05

13.03%

Since Inception

rr_AverageAnnualReturnSinceInception

8.03%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Return Before Taxes | Fidelity Mega Cap Stock Fund-Class C

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Class C - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

15.63%

Past 5 years

rr_AverageAnnualReturnYear05

13.28%

Since Inception

rr_AverageAnnualReturnSinceInception

7.90%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Return Before Taxes | Fidelity Mega Cap Stock Fund- Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Class I - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

17.77%

Past 5 years

rr_AverageAnnualReturnYear05

14.42%

Since Inception

rr_AverageAnnualReturnSinceInception

9.00%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Return Before Taxes | Fidelity Mega Cap Stock Fund-Class Z Equity

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Class Z - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

17.97%

Past 5 years

rr_AverageAnnualReturnYear05

Since Inception

rr_AverageAnnualReturnSinceInception

11.72%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 13, 2013

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | After Taxes on Distributions | Fidelity Mega Cap Stock Fund-Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

6.74%

Past 5 years

rr_AverageAnnualReturnYear05

11.30%

Since Inception

rr_AverageAnnualReturnSinceInception

7.25%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | After Taxes on Distributions and Sales | Fidelity Mega Cap Stock Fund-Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

8.97%

Past 5 years

rr_AverageAnnualReturnYear05

10.01%

Since Inception

rr_AverageAnnualReturnSinceInception

6.44%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | S&P 500® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

21.83%

Past 5 years

rr_AverageAnnualReturnYear05

15.79%

Since Inception

rr_AverageAnnualReturnSinceInception

9.60%

^[3]

06.30 Fidelity Mega Cap Stock Fund AMCIZ PRO-07 | Fidelity® Mega Cap Stock Fund | Russell Top 200® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

22.96%

Past 5 years

rr_AverageAnnualReturnYear05

16.01%

Since Inception

rr_AverageAnnualReturnSinceInception

9.50%

^[3]

[1] Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

[2] On Class C shares redeemed less than one year after purchase.

[3] From February 5, 2008 for Class A, Class M, Class C, and Class I; and August 13, 2013 for Class Z.

XML

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund

Fund Summary

Fund/Class:
Fidelity® Mega Cap Stock Fund/Fidelity® Mega Cap Stock Fund

Investment Objective

The fund seeks high total return through a combination of current income and capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

Shareholder Fees {- Fidelity® Mega Cap Stock Fund}	06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 Fidelity® Mega Cap Stock Fund USD ($)
(fees paid directly from your investment)	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Mega Cap Stock Fund}	06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 Fidelity® Mega Cap Stock Fund Fidelity Mega Cap Stock Fund-Retail Class
Management fee	0.44%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.24%
Total annual operating expenses	0.68%

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:

Sell All Shares

Expense Example {- Fidelity® Mega Cap Stock Fund}	06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 Fidelity® Mega Cap Stock Fund Fidelity Mega Cap Stock Fund-Retail Class USD ($)
1 year	$ 69
3 years	218
5 years	379
10 years	$ 847

Portfolio Turnover

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 39% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing at least 80% of assets in common stocks of companies with mega market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the Russell Top 200^® Index or the S&P 100^® Index).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

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.

Performance

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 an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for more recent performance information.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	18.52%	June 30, 2009
Lowest Quarter Return	-21.33%	December 31, 2008
Year-to-Date Return	0.52%	June 30, 2018

Average Annual Returns

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).

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity® Mega Cap Stock Fund} - 06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 - Fidelity® Mega Cap Stock Fund	Past 1 year	Past 5 years	Past 10 years
Fidelity Mega Cap Stock Fund-Retail Class | Return Before Taxes	17.77%	14.43%	7.90%
Fidelity Mega Cap Stock Fund-Retail Class | After Taxes on Distributions	13.50%	12.90%	7.06%
Fidelity Mega Cap Stock Fund-Retail Class | After Taxes on Distributions and Sales	13.15%	11.40%	6.30%
S&P 500® Index(reflects no deduction for fees, expenses, or taxes)	21.83%	15.79%	8.50%
Russell Top 200® Index(reflects no deduction for fees, expenses, or taxes)	22.96%	16.01%	8.39%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Mega Cap Stock Fund/Fidelity® Mega Cap Stock Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks high total return through a combination of current income and capital appreciation.

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 Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

rr_ShareholderFeeOther

none

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 39% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

39.00%

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

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing at least 80% of assets in common stocks of companies with mega market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the Russell Top 200^® Index or the S&P 100^® Index).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

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

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.

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 an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for more recent performance 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 an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.fidelity.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

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 Return	18.52%	June 30, 2009
Lowest Quarter Return	-21.33%	December 31, 2008
Year-to-Date Return	0.52%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

For the periods ended December 31, 2017

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund | Fidelity Mega Cap Stock Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Management fee

rr_ManagementFeesOverAssets

0.44%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual operating expenses

rr_ExpensesOverAssets

0.68%

1 year

rr_ExpenseExampleYear01

$ 69

3 years

rr_ExpenseExampleYear03

218

5 years

rr_ExpenseExampleYear05

379

10 years

rr_ExpenseExampleYear10

$ 847

2008

rr_AnnualReturn2008

(39.41%)

2009

rr_AnnualReturn2009

28.61%

2010

rr_AnnualReturn2010

14.41%

2011

rr_AnnualReturn2011

2.34%

2012

rr_AnnualReturn2012

19.42%

2013

rr_AnnualReturn2013

33.23%

2014

rr_AnnualReturn2014

11.66%

2015

rr_AnnualReturn2015

(1.43%)

2016

rr_AnnualReturn2016

13.63%

2017

rr_AnnualReturn2017

17.77%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

0.52%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.52%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(21.33%)

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund | Return Before Taxes | Fidelity Mega Cap Stock Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

17.77%

Past 5 years

rr_AverageAnnualReturnYear05

14.43%

Past 10 years

rr_AverageAnnualReturnYear10

7.90%

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund | After Taxes on Distributions | Fidelity Mega Cap Stock Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

13.50%

Past 5 years

rr_AverageAnnualReturnYear05

12.90%

Past 10 years

rr_AverageAnnualReturnYear10

7.06%

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund | After Taxes on Distributions and Sales | Fidelity Mega Cap Stock Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

13.15%

Past 5 years

rr_AverageAnnualReturnYear05

11.40%

Past 10 years

rr_AverageAnnualReturnYear10

6.30%

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund | S&P 500® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

21.83%

Past 5 years

rr_AverageAnnualReturnYear05

15.79%

Past 10 years

rr_AverageAnnualReturnYear10

8.50%

06.30 Fidelity Mega Cap Stock Fund Retail PRO-04 | Fidelity® Mega Cap Stock Fund | Russell Top 200® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

22.96%

Past 5 years

rr_AverageAnnualReturnYear05

16.01%

Past 10 years

rr_AverageAnnualReturnYear10

8.39%

XML

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund

Fund Summary

Fund:
Fidelity Advisor® Series Growth & Income Fund

Investment Objective

The fund seeks high total return through a combination of current income and capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

Shareholder Fees {- Fidelity Advisor® Series Growth & Income Fund}	06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 Fidelity Advisor® Series Growth & Income Fund USD ($)
(fees paid directly from your investment)	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity Advisor® Series Growth & Income Fund}	06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 Fidelity Advisor® Series Growth & Income Fund Fidelity Advisor Series Growth & Income Fund-Default
Management fee	none
Distribution and/or Service (12b-1) fees	none
Other expenses	0.01%
Total annual operating expenses	0.01%

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:

Sell All Shares

Expense Example {- Fidelity Advisor® Series Growth & Income Fund}	06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 Fidelity Advisor® Series Growth & Income Fund Fidelity Advisor Series Growth & Income Fund-Default USD ($)
1 year	$ 1
3 years	3
5 years	6
10 years	$ 13

Portfolio Turnover

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 42% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing a majority of assets in common stocks with a focus on those that pay current dividends and show potential for capital appreciation.

• Potentially investing in bonds, including lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds), as well as stocks that are not currently paying dividends, but offer prospects for future income or capital appreciation.

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities 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.

• 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.

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.

Performance

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 an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Prior to August 1, 2013, the fund was named Fidelity Advisor^® Series Mega Cap Fund, and the fund operated under certain different investment policies and compared its performance to a different additional index. The fund's historical performance may not represent its current investment policies. Past performance (before and after taxes) is not an indication of future performance.

Visit institutional.fidelity.com for more recent performance information.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	9.73%	March 31, 2013
Lowest Quarter Return	-9.32%	September 30, 2015
Year-to-Date Return	0.61%	June 30, 2018

Average Annual Returns

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).

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity Advisor® Series Growth & Income Fund} - 06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 - Fidelity Advisor® Series Growth & Income Fund	Past 1 year	Past 5 years	Since Inception	[1]	Inception Date
Fidelity Advisor Series Growth & Income Fund-Default					Dec. 06, 2012
Fidelity Advisor Series Growth & Income Fund-Default | Return Before Taxes	17.32%	14.10%	14.07%
Fidelity Advisor Series Growth & Income Fund-Default | After Taxes on Distributions	15.69%	12.71%	12.69%		Dec. 06, 2012
Fidelity Advisor Series Growth & Income Fund-Default | After Taxes on Distributions and Sales	10.84%	10.94%	10.92%		Dec. 06, 2012
S&P 500® Index(reflects no deduction for fees, expenses, or taxes)	21.83%	15.79%	15.78%
Fidelity Series Growth & Income Fund Linked Index℠(reflects no deduction for fees, expenses, or taxes)	21.83%	15.69%	15.61%

[1] From December 6, 2012

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund:
Fidelity Advisor® Series Growth & Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks high total return through a combination of current income and capital appreciation.

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 Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

rr_ShareholderFeeOther

none

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 42% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

42.00%

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

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing a majority of assets in common stocks with a focus on those that pay current dividends and show potential for capital appreciation.

• Potentially investing in bonds, including lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds), as well as stocks that are not currently paying dividends, but offer prospects for future income or capital appreciation.

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities 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.

• 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.

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

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.

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 an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Prior to August 1, 2013, the fund was named Fidelity Advisor^® Series Mega Cap Fund, and the fund operated under certain different investment policies and compared its performance to a different additional index. The fund's historical performance may not represent its current investment policies. Past performance (before and after taxes) is not an indication of future performance.

Visit institutional.fidelity.com for more recent performance 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 an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

institutional.fidelity.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

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 Return	9.73%	March 31, 2013
Lowest Quarter Return	-9.32%	September 30, 2015
Year-to-Date Return	0.61%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

For the periods ended December 31, 2017

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund | Fidelity Advisor Series Growth & Income Fund-Default

Risk/Return:

rr_RiskReturnAbstract

Management fee

rr_ManagementFeesOverAssets

none

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.01%

Total annual operating expenses

rr_ExpensesOverAssets

0.01%

1 year

rr_ExpenseExampleYear01

$ 1

3 years

rr_ExpenseExampleYear03

3

5 years

rr_ExpenseExampleYear05

6

10 years

rr_ExpenseExampleYear10

$ 13

2013

rr_AnnualReturn2013

32.36%

2014

rr_AnnualReturn2014

10.13%

2015

rr_AnnualReturn2015

(2.37%)

2016

rr_AnnualReturn2016

15.84%

2017

rr_AnnualReturn2017

17.32%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

0.61%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2013

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.73%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2015

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(9.32%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund | Return Before Taxes | Fidelity Advisor Series Growth & Income Fund-Default

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Advisor® Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

17.32%

Past 5 years

rr_AverageAnnualReturnYear05

14.10%

Since Inception

rr_AverageAnnualReturnSinceInception

14.07%

^[1]

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund | After Taxes on Distributions | Fidelity Advisor Series Growth & Income Fund-Default

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Advisor® Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

15.69%

Past 5 years

rr_AverageAnnualReturnYear05

12.71%

Since Inception

rr_AverageAnnualReturnSinceInception

12.69%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund | After Taxes on Distributions and Sales | Fidelity Advisor Series Growth & Income Fund-Default

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Advisor® Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

10.84%

Past 5 years

rr_AverageAnnualReturnYear05

10.94%

Since Inception

rr_AverageAnnualReturnSinceInception

10.92%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund | S&P 500® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

21.83%

Past 5 years

rr_AverageAnnualReturnYear05

15.79%

Since Inception

rr_AverageAnnualReturnSinceInception

15.78%

^[1]

06.30 Fidelity Advisor Series Growth & Income Fund PRO-04 | Fidelity Advisor® Series Growth & Income Fund | Fidelity Series Growth & Income Fund Linked Index℠(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

21.83%

Past 5 years

rr_AverageAnnualReturnYear05

15.69%

Since Inception

rr_AverageAnnualReturnSinceInception

15.61%

^[1]

[1] From December 6, 2012

XML

06.30 Fidelity Growth Discovery Fund K PRO-04 | Fidelity® Growth Discovery Fund

Fund Summary

Fund/Class:
Fidelity® Growth Discovery Fund/K

Investment Objective

The fund seeks capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

Shareholder Fees {- Fidelity® Growth Discovery Fund}	06.30 Fidelity Growth Discovery Fund K PRO-04 Fidelity® Growth Discovery Fund USD ($)
(fees paid directly from your investment)	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Growth Discovery Fund}	06.30 Fidelity Growth Discovery Fund K PRO-04 Fidelity® Growth Discovery Fund Fidelity Growth Discovery Fund-Class K
Management fee (fluctuates based on the fund's performance relative to a securities market index)	0.54%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.09%
Total annual operating expenses	0.63%

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:

Sell All Shares

Expense Example {- Fidelity® Growth Discovery Fund}	06.30 Fidelity Growth Discovery Fund K PRO-04 Fidelity® Growth Discovery Fund Fidelity Growth Discovery Fund-Class K USD ($)
1 year	$ 64
3 years	202
5 years	351
10 years	$ 786

Portfolio Turnover

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 45% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in common stocks.

• Investing in companies that Fidelity Management & Research Company (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks).

• Investing in domestic and foreign issuers.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

• "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.

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.

Performance

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 is not an indication of future performance.

Visit www.401k.com and log in for more recent performance information.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	16.48%	March 31, 2012
Lowest Quarter Return	-15.48%	September 30, 2011
Year-to-Date Return	9.86%	June 30, 2018

Average Annual Returns

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity® Growth Discovery Fund} - 06.30 Fidelity Growth Discovery Fund K PRO-04 - Fidelity® Growth Discovery Fund	Past 1 year	Past 5 years	Since Inception	[1]	Inception Date
Fidelity Growth Discovery Fund-Class K					May 09, 2008
Fidelity Growth Discovery Fund-Class K | Return Before Taxes	34.83%	17.33%	9.51%
Russell 3000® Growth Index(reflects no deduction for fees, expenses, or taxes)	29.59%	17.16%	10.86%

[1] From May 9, 2008

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Growth Discovery Fund K PRO-04 | Fidelity® Growth Discovery Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Growth Discovery Fund/K

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks capital appreciation.

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 Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

rr_ShareholderFeeOther

none

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 45% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

45.00%

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

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in common stocks.

• Investing in companies that Fidelity Management & Research Company (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks).

• Investing in domestic and foreign issuers.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

• "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.

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

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.

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 over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance is not an indication of future performance.

Visit www.401k.com and log in for more recent performance 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 over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.401k.com and log in

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance is not an indication of future performance.

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 Return	16.48%	March 31, 2012
Lowest Quarter Return	-15.48%	September 30, 2011
Year-to-Date Return	9.86%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

For the periods ended December 31, 2017

06.30 Fidelity Growth Discovery Fund K PRO-04 | Fidelity® Growth Discovery Fund | Fidelity Growth Discovery Fund-Class K

Risk/Return:

rr_RiskReturnAbstract

Management fee (fluctuates based on the fund's performance relative to a securities market index)

rr_ManagementFeesOverAssets

0.54%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.09%

Total annual operating expenses

rr_ExpensesOverAssets

0.63%

1 year

rr_ExpenseExampleYear01

$ 64

3 years

rr_ExpenseExampleYear03

202

5 years

rr_ExpenseExampleYear05

351

10 years

rr_ExpenseExampleYear10

$ 786

2009

rr_AnnualReturn2009

29.70%

2010

rr_AnnualReturn2010

24.33%

2011

rr_AnnualReturn2011

0.70%

2012

rr_AnnualReturn2012

14.70%

2013

rr_AnnualReturn2013

36.72%

2014

rr_AnnualReturn2014

11.48%

2015

rr_AnnualReturn2015

7.29%

2016

rr_AnnualReturn2016

0.83%

2017

rr_AnnualReturn2017

34.83%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

9.86%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.48%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(15.48%)

Inception Date

rr_AverageAnnualReturnInceptionDate

May 09, 2008

06.30 Fidelity Growth Discovery Fund K PRO-04 | Fidelity® Growth Discovery Fund | Return Before Taxes | Fidelity Growth Discovery Fund-Class K

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Growth Discovery Fund

Label

rr_AverageAnnualReturnLabel

Class K

Past 1 year

rr_AverageAnnualReturnYear01

34.83%

Past 5 years

rr_AverageAnnualReturnYear05

17.33%

Since Inception

rr_AverageAnnualReturnSinceInception

9.51%

^[1]

06.30 Fidelity Growth Discovery Fund K PRO-04 | Fidelity® Growth Discovery Fund | Russell 3000® Growth Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

29.59%

Past 5 years

rr_AverageAnnualReturnYear05

17.16%

Since Inception

rr_AverageAnnualReturnSinceInception

10.86%

^[1]

[1] From May 9, 2008

XML

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund

Fund Summary

Fund/Class:
Fidelity® Growth Discovery Fund/Fidelity® Growth Discovery Fund

Investment Objective

The fund seeks capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

Shareholder Fees {- Fidelity® Growth Discovery Fund}	06.30 Fidelity Growth Discovery Fund Retail PRO-04 Fidelity® Growth Discovery Fund USD ($)
(fees paid directly from your investment)	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Growth Discovery Fund}	06.30 Fidelity Growth Discovery Fund Retail PRO-04 Fidelity® Growth Discovery Fund Fidelity Growth Discovery Fund-Retail Class
Management fee (fluctuates based on the fund's performance relative to a securities market index)	0.54%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.20%
Total annual operating expenses	0.74%

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:

Sell All Shares

Expense Example {- Fidelity® Growth Discovery Fund}	06.30 Fidelity Growth Discovery Fund Retail PRO-04 Fidelity® Growth Discovery Fund Fidelity Growth Discovery Fund-Retail Class USD ($)
1 year	$ 76
3 years	237
5 years	411
10 years	$ 918

Portfolio Turnover

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 45% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in common stocks.

• Investing in companies that Fidelity Management & Research Company (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks).

• Investing in domestic and foreign issuers.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

• "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.

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.

Performance

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.

Visit www.fidelity.com for more recent performance information.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	16.40%	March 31, 2012
Lowest Quarter Return	-27.00%	December 31, 2008
Year-to-Date Return	9.80%	June 30, 2018

Average Annual Returns

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).

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity® Growth Discovery Fund} - 06.30 Fidelity Growth Discovery Fund Retail PRO-04 - Fidelity® Growth Discovery Fund	Past 1 year	Past 5 years	Past 10 years
Fidelity Growth Discovery Fund-Retail Class | Return Before Taxes	34.70%	17.17%	8.07%
Fidelity Growth Discovery Fund-Retail Class | After Taxes on Distributions	33.11%	16.87%	7.88%
Fidelity Growth Discovery Fund-Retail Class | After Taxes on Distributions and Sales	20.86%	13.93%	6.57%
Russell 3000® Growth Index(reflects no deduction for fees, expenses, or taxes)	29.59%	17.16%	9.93%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Growth Discovery Fund/Fidelity® Growth Discovery Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks capital appreciation.

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 Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

rr_ShareholderFeeOther

none

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 45% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

45.00%

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

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in common stocks.

• Investing in companies that Fidelity Management & Research Company (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks).

• Investing in domestic and foreign issuers.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities can react differently to these developments.

• 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.

• 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.

• "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.

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

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.

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 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.

Visit www.fidelity.com for more recent performance 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 over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.fidelity.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

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 Return	16.40%	March 31, 2012
Lowest Quarter Return	-27.00%	December 31, 2008
Year-to-Date Return	9.80%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

For the periods ended December 31, 2017

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund | Fidelity Growth Discovery Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Management fee (fluctuates based on the fund's performance relative to a securities market index)

rr_ManagementFeesOverAssets

0.54%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.20%

Total annual operating expenses

rr_ExpensesOverAssets

0.74%

1 year

rr_ExpenseExampleYear01

$ 76

3 years

rr_ExpenseExampleYear03

237

5 years

rr_ExpenseExampleYear05

411

10 years

rr_ExpenseExampleYear10

$ 918

2008

rr_AnnualReturn2008

(46.72%)

2009

rr_AnnualReturn2009

29.33%

2010

rr_AnnualReturn2010

24.04%

2011

rr_AnnualReturn2011

0.50%

2012

rr_AnnualReturn2012

14.50%

2013

rr_AnnualReturn2013

36.47%

2014

rr_AnnualReturn2014

11.37%

2015

rr_AnnualReturn2015

7.16%

2016

rr_AnnualReturn2016

0.68%

2017

rr_AnnualReturn2017

34.70%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

9.80%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.40%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(27.00%)

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund | Return Before Taxes | Fidelity Growth Discovery Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Growth Discovery Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

34.70%

Past 5 years

rr_AverageAnnualReturnYear05

17.17%

Past 10 years

rr_AverageAnnualReturnYear10

8.07%

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund | After Taxes on Distributions | Fidelity Growth Discovery Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Growth Discovery Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

33.11%

Past 5 years

rr_AverageAnnualReturnYear05

16.87%

Past 10 years

rr_AverageAnnualReturnYear10

7.88%

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund | After Taxes on Distributions and Sales | Fidelity Growth Discovery Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Growth Discovery Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

20.86%

Past 5 years

rr_AverageAnnualReturnYear05

13.93%

Past 10 years

rr_AverageAnnualReturnYear10

6.57%

06.30 Fidelity Growth Discovery Fund Retail PRO-04 | Fidelity® Growth Discovery Fund | Russell 3000® Growth Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

29.59%

Past 5 years

rr_AverageAnnualReturnYear05

17.16%

Past 10 years

rr_AverageAnnualReturnYear10

9.93%

XML

06.30 Fidelity Fund Class K PRO-05 | Fidelity® Fund

Fund Summary

Fund/Class:
Fidelity® Fund/K

Investment Objective

The fund seeks long-term capital growth.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

Shareholder Fees {- Fidelity® Fund}	06.30 Fidelity Fund Class K PRO-05 Fidelity® Fund USD ($)
(fees paid directly from your investment)	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Fund}	06.30 Fidelity Fund Class K PRO-05 Fidelity® Fund Fidelity Fund-Class K
Management fee	0.33%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.08%
Total annual operating expenses	0.41%

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:

Sell All Shares

Expense Example {- Fidelity® Fund}	06.30 Fidelity Fund Class K PRO-05 Fidelity® Fund Fidelity Fund-Class K USD ($)
1 year	$ 42
3 years	132
5 years	230
10 years	$ 518

Portfolio Turnover

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 38% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in common stocks.

• Potentially investing a portion of assets in bonds, including lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities 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.

• 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.

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.

Performance

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 is not an indication of future performance.

Visit www.401k.com and log in for more recent performance information.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	16.20%	June 30, 2009
Lowest Quarter Return	-15.04%	September 30, 2011
Year-to-Date Return	3.65%	June 30, 2018

Average Annual Returns

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity® Fund} - 06.30 Fidelity Fund Class K PRO-05 - Fidelity® Fund	Past 1 year	Past 5 years	Since Inception	[1]	Inception Date
Fidelity Fund-Class K					May 09, 2008
Fidelity Fund-Class K | Return Before Taxes	23.95%	14.45%	7.80%
S&P 500® Index(reflects no deduction for fees, expenses, or taxes)	21.83%	15.79%	9.37%

[1] From May 9, 2008

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Fund Class K PRO-05 | Fidelity® Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Fund/K

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks long-term capital growth.

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 Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

rr_ShareholderFeeOther

none

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 38% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

38.00%

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

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in common stocks.

• Potentially investing a portion of assets in bonds, including lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities 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.

• 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.

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

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.

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 over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance is not an indication of future performance.

Visit www.401k.com and log in for more recent performance 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 over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.401k.com and log in

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance is not an indication of future performance.

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 Return	16.20%	June 30, 2009
Lowest Quarter Return	-15.04%	September 30, 2011
Year-to-Date Return	3.65%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

For the periods ended December 31, 2017

06.30 Fidelity Fund Class K PRO-05 | Fidelity® Fund | Fidelity Fund-Class K

Risk/Return:

rr_RiskReturnAbstract

Management fee

rr_ManagementFeesOverAssets

0.33%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.08%

Total annual operating expenses

rr_ExpensesOverAssets

0.41%

1 year

rr_ExpenseExampleYear01

$ 42

3 years

rr_ExpenseExampleYear03

132

5 years

rr_ExpenseExampleYear05

230

10 years

rr_ExpenseExampleYear10

$ 518

2009

rr_AnnualReturn2009

26.95%

2010

rr_AnnualReturn2010

14.74%

2011

rr_AnnualReturn2011

(2.19%)

2012

rr_AnnualReturn2012

16.72%

2013

rr_AnnualReturn2013

29.18%

2014

rr_AnnualReturn2014

12.98%

2015

rr_AnnualReturn2015

3.47%

2016

rr_AnnualReturn2016

4.93%

2017

rr_AnnualReturn2017

23.95%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

3.65%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.20%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(15.04%)

Inception Date

rr_AverageAnnualReturnInceptionDate

May 09, 2008

06.30 Fidelity Fund Class K PRO-05 | Fidelity® Fund | Return Before Taxes | Fidelity Fund-Class K

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Fund

Label

rr_AverageAnnualReturnLabel

Class K

Past 1 year

rr_AverageAnnualReturnYear01

23.95%

Past 5 years

rr_AverageAnnualReturnYear05

14.45%

Since Inception

rr_AverageAnnualReturnSinceInception

7.80%

^[1]

06.30 Fidelity Fund Class K PRO-05 | Fidelity® Fund | S&P 500® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

21.83%

Past 5 years

rr_AverageAnnualReturnYear05

15.79%

Since Inception

rr_AverageAnnualReturnSinceInception

9.37%

^[1]

[1] From May 9, 2008

XML

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund

Fund Summary

Fund/Class:
Fidelity® Fund/Fidelity® Fund

Investment Objective

The fund seeks long-term capital growth.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

Shareholder Fees {- Fidelity® Fund}	06.30 Fidelity Fund Retail PRO-05 Fidelity® Fund USD ($)
(fees paid directly from your investment)	none

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Fund}	06.30 Fidelity Fund Retail PRO-05 Fidelity® Fund Fidelity Fund-Retail Class
Management fee	0.33%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.17%
Total annual operating expenses	0.50%

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:

Sell All Shares

Expense Example {- Fidelity® Fund}	06.30 Fidelity Fund Retail PRO-05 Fidelity® Fund Fidelity Fund-Retail Class USD ($)
1 year	$ 51
3 years	160
5 years	280
10 years	$ 628

Portfolio Turnover

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 38% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in common stocks.

• Potentially investing a portion of assets in bonds, including lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• 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, including different market sectors, and different types of securities 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.

• 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.

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.

Performance

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.

Visit www.fidelity.com for more recent performance information.

Year-by-Year Returns

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	16.14%	June 30, 2009
Lowest Quarter Return	-22.64%	December 31, 2008
Year-to-Date Return	3.60%	June 30, 2018

Average Annual Returns

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).

For the periods ended December 31, 2017

Average Annual Total Returns{- Fidelity® Fund} - 06.30 Fidelity Fund Retail PRO-05 - Fidelity® Fund	Past 1 year	Past 5 years	Past 10 years
Fidelity Fund-Retail Class | Return Before Taxes	23.82%	14.32%	6.77%
Fidelity Fund-Retail Class | After Taxes on Distributions	20.46%	11.97%	5.52%
Fidelity Fund-Retail Class | After Taxes on Distributions and Sales	15.87%	11.02%	5.21%
S&P 500® Index(reflects no deduction for fees, expenses, or taxes)	21.83%	15.79%	8.50%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2018

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Fund/Fidelity® Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks long-term capital growth.

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 Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

rr_ShareholderFeeOther

none

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 38% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

38.00%

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

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in common stocks.

• Potentially investing a portion of assets in bonds, including lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds).

• Investing in domestic and foreign issuers.

• Investing in either "growth" stocks or "value" stocks or both.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• 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, including different market sectors, and different types of securities 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.

• 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.

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

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.

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 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.

Visit www.fidelity.com for more recent performance 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 over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.fidelity.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

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 Return	16.14%	June 30, 2009
Lowest Quarter Return	-22.64%	December 31, 2008
Year-to-Date Return	3.60%	June 30, 2018

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

For the periods ended December 31, 2017

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund | Fidelity Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Management fee

rr_ManagementFeesOverAssets

0.33%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.17%

Total annual operating expenses

rr_ExpensesOverAssets

0.50%

1 year

rr_ExpenseExampleYear01

$ 51

3 years

rr_ExpenseExampleYear03

160

5 years

rr_ExpenseExampleYear05

280

10 years

rr_ExpenseExampleYear10

$ 628

2008

rr_AnnualReturn2008

(40.33%)

2009

rr_AnnualReturn2009

26.75%

2010

rr_AnnualReturn2010

14.55%

2011

rr_AnnualReturn2011

(2.36%)

2012

rr_AnnualReturn2012

16.57%

2013

rr_AnnualReturn2013

29.01%

2014

rr_AnnualReturn2014

12.85%

2015

rr_AnnualReturn2015

3.35%

2016

rr_AnnualReturn2016

4.82%

2017

rr_AnnualReturn2017

23.82%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

3.60%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.14%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(22.64%)

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund | Return Before Taxes | Fidelity Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

23.82%

Past 5 years

rr_AverageAnnualReturnYear05

14.32%

Past 10 years

rr_AverageAnnualReturnYear10

6.77%

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund | After Taxes on Distributions | Fidelity Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

20.46%

Past 5 years

rr_AverageAnnualReturnYear05

11.97%

Past 10 years

rr_AverageAnnualReturnYear10

5.52%

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund | After Taxes on Distributions and Sales | Fidelity Fund-Retail Class

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

15.87%

Past 5 years

rr_AverageAnnualReturnYear05

11.02%

Past 10 years

rr_AverageAnnualReturnYear10

5.21%

06.30 Fidelity Fund Retail PRO-05 | Fidelity® Fund | S&P 500® Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

21.83%

Past 5 years

rr_AverageAnnualReturnYear05

15.79%

Past 10 years

rr_AverageAnnualReturnYear10

8.50%

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY HASTINGS STREET TRUST
Prospectus Date	rr_ProspectusDate	Aug. 29, 2018
Document Creation Date	dei_DocumentCreationDate	Aug. 27, 2018