485BPOS

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM N-1A
REGISTRATION STATEMENT (No. 002-11517)
	UNDER THE SECURITIES ACT OF 1933	[X]
	Pre-Effective Amendment No. ____	[ ]
	Post-Effective Amendment No. 156	[X]
and
REGISTRATION STATEMENT (No. 811-00215)
	UNDER THE INVESTMENT COMPANY ACT OF 1940	[X]
	Amendment No. 156	[X]
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
Scott C. Goebel, 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).

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. 156 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 16th day of September 2015.

	Fidelity Hastings Street Trust
	By	/s/Kenneth B. Robins
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||		Kenneth B. Robins, 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/Kenneth B. Robins		President and Treasurer	September 16, 2015
Kenneth B. Robins		(Principal Executive Officer)
/s/Howard J. Galligan III		Chief Financial Officer	September 16, 2015
Howard J. Galligan III		(Principal Financial Officer)
/s/James C. Curvey	*	Trustee	September 16, 2015
James C. Curvey
/s/Dennis J. Dirks	*	Trustee	September 16, 2015
Dennis J. Dirks
/s/Alan J. Lacy	*	Trustee	September 16, 2015
Alan J. Lacy
/s/Ned C. Lautenbach	*	Trustee	September 16, 2015
Ned C. Lautenbach
/s/Joseph Mauriello	*	Trustee	September 16, 2015
Joseph Mauriello
/s/Charles S. Morrison	*	Trustee	September 16, 2015
Charles S. Morrison
/s/Robert W. Selander	*	Trustee	September 16, 2015
Robert W. Selander
/s/Cornelia M. Small	*	Trustee	September 16, 2015
Cornelia M. Small
/s/William S. Stavropoulos	*	Trustee	September 16, 2015
William S. Stavropoulos
/s/David M. Thomas	*	Trustee	September 16, 2015
David M. Thomas

*	By:	/s/Megan C. Johnson
		Megan C. Johnson, pursuant to a power of attorney dated April 1, 2014 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 VIII Fidelity Beacon Street Trust Fidelity Capital Trust Fidelity Central Investment Portfolios LLC Fidelity Commonwealth Trust Fidelity Concord Street Trust Fidelity Congress Street Fund Fidelity Contrafund 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 Summer Street Trust Fidelity Trend Fund Variable Insurance Products Fund Variable Insurance Products Fund II Variable Insurance Products Fund III  

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, Joseph R. Fleming, 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 April 1, 2014.

WITNESS our hands on this first day of April 2014.

/s/James C. Curvey	/s/Charles S. Morrison
James C. Curvey	Charles S. Morrison
/s/Dennis J. Dirks	/s/Robert W. Selander
Dennis J. Dirks	Robert W. Selander
/s/Alan J. Lacy	/s/Cornelia M. Small
Alan J. Lacy	Cornelia M. Small
/s/Ned C. Lautenbach	/s/William S. Stavropoulos
Ned C. Lautenbach	William S. Stavropoulos
/s/Joseph Mauriello	/s/David M. Thomas
Joseph Mauriello	David M. Thomas

XML

Z | Fidelity Mega Cap Stock Fund

Fund Summary

Fund/Class:
Fidelity^® Mega Cap Stock Fund/Fidelity Advisor^® Mega Cap Stock Fund 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.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees	Z Fidelity Mega Cap Stock Fund Class Z USD ($)
Shareholder fees (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	Z Fidelity Mega Cap Stock Fund Class Z
Management fee	0.45%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.09%
Total annual operating expenses	0.54%

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	Z Fidelity Mega Cap Stock Fund Class Z USD ($)
1 year	$ 55
3 years	173
5 years	302
10 years	$ 677

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 22% 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 the performance of the fund's shares over the past 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 is not an indication of future performance.

Visit www.advisor.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Year

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	4.93%	June 30, 2014
Lowest Quarter Return	1.34%	September 30, 2014
Year-to-Date Return	1.46%	June 30, 2015

Average Annual Returns
For the periods ended
December 31, 2014

Average Annual Total Returns - Z - Fidelity Mega Cap Stock Fund	Past 1 year	Life of class	[1]	Inception Date
Class Z	11.75%	15.92%		Aug. 13, 2013
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	17.53%		Aug. 13, 2013
Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)	13.25%	17.64%		Aug. 13, 2013

[1] From August 13, 2013.

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K | 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
(fees paid directly from your investment)

Shareholder Fees	K Fidelity Growth Discovery Fund Class K USD ($)
Shareholder fees (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	K Fidelity Growth Discovery Fund Class K
Management fee (fluctuates based on the fund's performance relative to a securities market index)	0.55%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.09%
Total annual operating expenses	0.64%

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	K Fidelity Growth Discovery Fund Class K USD ($)
1 year	$ 65
3 years	205
5 years	357
10 years	$ 798

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 51% 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 updated return 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	5.63%	June 30, 2015

Average Annual Returns
For the periods ended
December 31, 2014

Average Annual Total Returns - K - Fidelity Growth Discovery Fund	Past 1 year	Past 5 years	Life of class	[1]	Inception Date
Class K	11.48%	16.96%	7.79%		May 09, 2008
Russell 3000® Growth Index (reflects no deduction for fees, expenses, or taxes)	12.44%	15.89%	9.69%		May 09, 2008

[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, 2015

Series | Fidelity Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Series Growth & Income Fund/Fidelity 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)

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 40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

40.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

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:

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 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 www.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and 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	9.77%	March 31, 2013
Lowest Quarter Return	0.42%	September 30, 2014
Year-to-Date Return	1.63%	June 30, 2015

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.

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.

For the periods ended
December 31, 2014

Series | Fidelity Series Growth & Income Fund | Class: Fidelity Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.18%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

Total annual operating expenses

^[1]

rr_ExpensesOverAssets

0.66%

1 year

rr_ExpenseExampleYear01

$ 67

3 years

rr_ExpenseExampleYear03

211

5 years

rr_ExpenseExampleYear05

368

10 years

rr_ExpenseExampleYear10

$ 822

2013

rr_AnnualReturn2013

32.40%

2014

rr_AnnualReturn2014

10.02%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.63%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2013

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.77%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2014

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.42%

Series | Fidelity Series Growth & Income Fund | Return Before Taxes | Class: Fidelity Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

10.02%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

20.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

Series | Fidelity Series Growth & Income Fund | Return After Taxes on Distributions | Class: Fidelity Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

8.50%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

18.69%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

Series | Fidelity Series Growth & Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

6.18%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

15.23%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

22.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

Series | Fidelity Series Growth & Income Fund | Fidelity Series Growth & Income Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Fidelity Series Growth & Income Fund Linked Index℠

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

22.01%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

[2] From December 6, 2012.

XML

Series | Fidelity Series Growth & Income Fund

Fund Summary

Fund/Class:
Fidelity^® Series Growth & Income Fund/Fidelity 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
(fees paid directly from your investment)

Shareholder Fees	Series Fidelity Series Growth & Income Fund Class: Fidelity Series Growth & Income Fund USD ($)
Shareholder fees (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		Series Fidelity Series Growth & Income Fund Class: Fidelity Series Growth & Income Fund
Management fee		0.45%
Distribution and/or Service (12b-1) fees		none
Other expenses		0.18%
Acquired fund fees and expenses		0.03%
Total annual operating expenses	[1]	0.66%

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	Series Fidelity Series Growth & Income Fund Class: Fidelity Series Growth & Income Fund USD ($)
1 year	$ 67
3 years	211
5 years	368
10 years	$ 822

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 40% 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 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 www.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	9.77%	March 31, 2013
Lowest Quarter Return	0.42%	September 30, 2014
Year-to-Date Return	1.63%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - Series - Fidelity Series Growth & Income Fund	Past 1 year	Life of class	[1]	Inception Date
Class: Fidelity Series Growth & Income Fund | Return Before Taxes	10.02%	20.18%		Dec. 06, 2012
Class: Fidelity Series Growth & Income Fund | Return After Taxes on Distributions	8.50%	18.69%		Dec. 06, 2012
Class: Fidelity Series Growth & Income Fund | Return After Taxes on Distributions and Sale of Fund Shares	6.18%	15.23%		Dec. 06, 2012
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	22.45%		Dec. 06, 2012
Fidelity Series Growth & Income Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)	13.69%	22.01%		Dec. 06, 2012

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

[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, 2015

K | 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)

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 51% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

51.00%

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:

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 updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.401k.com and log in for updated return information

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	5.63%	June 30, 2015

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns
For the periods ended
December 31, 2014

K | Fidelity Growth Discovery Fund | Class K

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

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

rr_ManagementFeesOverAssets

0.55%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.09%

Total annual operating expenses

rr_ExpensesOverAssets

0.64%

1 year

rr_ExpenseExampleYear01

$ 65

3 years

rr_ExpenseExampleYear03

205

5 years

rr_ExpenseExampleYear05

357

10 years

rr_ExpenseExampleYear10

$ 798

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%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

5.63%

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%)

Label

rr_AverageAnnualReturnLabel

Class K

Past 1 year

rr_AverageAnnualReturnYear01

11.48%

Past 5 years

rr_AverageAnnualReturnYear05

16.96%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

7.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 09, 2008

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Russell 3000^® Growth Index

Past 1 year

rr_AverageAnnualReturnYear01

12.44%

Past 5 years

rr_AverageAnnualReturnYear05

15.89%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

9.69%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 09, 2008

[1] From May 9, 2008.

XML

Retail | 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
(fees paid directly from your investment)

Shareholder Fees	Retail Fidelity Fund Class: Fidelity Fund USD ($)
Shareholder fees (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	Retail Fidelity Fund Class: Fidelity Fund
Management fee	0.34%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.18%
Total annual operating expenses	0.52%

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	Retail Fidelity Fund Class: Fidelity Fund USD ($)
1 year	$ 53
3 years	167
5 years	291
10 years	$ 653

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 59% 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 updated return 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	4.29%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - Retail - Fidelity Fund	Past 1 year	Past 5 years	Past 10 years
Class: Fidelity Fund | Return Before Taxes	12.85%	13.68%	7.44%
Class: Fidelity Fund | Return After Taxes on Distributions	9.60%	12.48%	6.67%
Class: Fidelity Fund | Return After Taxes on Distributions and Sale of Fund Shares	9.27%	10.84%	5.99%
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	15.45%	7.67%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

A T B C | 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, T, B, C

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.

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 (Click Here) 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 22% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.00%

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.

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 www.advisor.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.advisor.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

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.

Calendar Years

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	1.16%	June 30, 2015

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.

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 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.

For the periods ended
December 31, 2014

A T B C | 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)

^[1]

rr_MaximumDeferredSalesChargeOverOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.35%

Total annual operating expenses

rr_ExpensesOverAssets

1.05%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

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

1 year

rr_ExpenseExampleYear01

$ 676

3 years

rr_ExpenseExampleYear03

890

5 years

rr_ExpenseExampleYear05

1,121

10 years

rr_ExpenseExampleYear10

1,784

1 year

rr_ExpenseExampleNoRedemptionYear01

676

3 years

rr_ExpenseExampleNoRedemptionYear03

890

5 years

rr_ExpenseExampleNoRedemptionYear05

1,121

10 years

rr_ExpenseExampleNoRedemptionYear10

$ 1,784

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%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.16%

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%)

A T B C | Fidelity Mega Cap Stock Fund | Class T

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)

^[1]

rr_MaximumDeferredSalesChargeOverOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other expenses

rr_OtherExpensesOverAssets

0.26%

Total annual operating expenses

rr_ExpensesOverAssets

1.21%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

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

1 year

rr_ExpenseExampleYear01

$ 469

3 years

rr_ExpenseExampleYear03

721

5 years

rr_ExpenseExampleYear05

992

10 years

rr_ExpenseExampleYear10

1,765

1 year

rr_ExpenseExampleNoRedemptionYear01

469

3 years

rr_ExpenseExampleNoRedemptionYear03

721

5 years

rr_ExpenseExampleNoRedemptionYear05

992

10 years

rr_ExpenseExampleNoRedemptionYear10

$ 1,765

A T B C | Fidelity Mega Cap Stock Fund | Class B

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)

^[2]

rr_MaximumDeferredSalesChargeOverOther

5.00%

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.28%

Total annual operating expenses

rr_ExpensesOverAssets

1.73%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

Declines over 6 years from 5.00% to 0%.

1 year

rr_ExpenseExampleYear01

$ 676

3 years

rr_ExpenseExampleYear03

845

5 years

rr_ExpenseExampleYear05

1,139

10 years

rr_ExpenseExampleYear10

1,777

1 year

rr_ExpenseExampleNoRedemptionYear01

176

3 years

rr_ExpenseExampleNoRedemptionYear03

545

5 years

rr_ExpenseExampleNoRedemptionYear05

939

10 years

rr_ExpenseExampleNoRedemptionYear10

$ 1,777

A T B C | 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)

^[3]

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.25%

Total annual operating expenses

rr_ExpensesOverAssets

1.70%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

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

1 year

rr_ExpenseExampleYear01

$ 273

3 years

rr_ExpenseExampleYear03

536

5 years

rr_ExpenseExampleYear05

923

10 years

rr_ExpenseExampleYear10

2,009

1 year

rr_ExpenseExampleNoRedemptionYear01

173

3 years

rr_ExpenseExampleNoRedemptionYear03

536

5 years

rr_ExpenseExampleNoRedemptionYear05

923

10 years

rr_ExpenseExampleNoRedemptionYear10

$ 2,009

A T B C | Fidelity Mega Cap Stock Fund | Return Before Taxes | Class A

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

4.83%

Past 5 years

rr_AverageAnnualReturnYear05

14.08%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

7.48%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | Return Before Taxes | Class T

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class T - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

7.16%

Past 5 years

rr_AverageAnnualReturnYear05

14.32%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

7.58%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | Return Before Taxes | Class B

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class B - ReturnBefore Taxes

Past 1 year

rr_AverageAnnualReturnYear01

5.48%

Past 5 years

rr_AverageAnnualReturnYear05

14.30%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

7.58%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | Return Before Taxes | Class C

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class C - Return BeforeTaxes

Past 1 year

rr_AverageAnnualReturnYear01

9.52%

Past 5 years

rr_AverageAnnualReturnYear05

14.58%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

7.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions | Class A

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A - Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

3.83%

Past 5 years

rr_AverageAnnualReturnYear05

13.63%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

7.11%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class A

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A - Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

3.49%

Past 5 years

rr_AverageAnnualReturnYear05

11.30%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

5.94%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | S&P 500® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Past 5 years

rr_AverageAnnualReturnYear05

15.45%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

8.82%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

A T B C | Fidelity Mega Cap Stock Fund | Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Russell Top 200^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.25%

Past 5 years

rr_AverageAnnualReturnYear05

15.01%

Life of class

^[4]

rr_AverageAnnualReturnSinceInception

8.48%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

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

[2] Declines over 6 years from 5.00% to 0%.

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

[4] From February 5, 2008.

XML

I | Fidelity Mega Cap Stock Fund

Fund Summary

Fund/Class:
Fidelity^® Mega Cap Stock Fund/Fidelity Advisor^® Mega Cap Stock Fund I

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
(fees paid directly from your investment)

Shareholder Fees	I Fidelity Mega Cap Stock Fund Class I USD ($)
Shareholder fees (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	I Fidelity Mega Cap Stock Fund Class I
Management fee	0.45%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.24%
Total annual operating expenses	0.69%

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	I Fidelity Mega Cap Stock Fund Class I USD ($)
1 year	$ 70
3 years	221
5 years	384
10 years	$ 859

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 22% 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.advisor.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	18.36%	June 30, 2009
Lowest Quarter Return	-13.08%	September 30, 2011
Year-to-Date Return	1.33%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - I - Fidelity Mega Cap Stock Fund	Past 1 year	Past 5 years	Life of class	[1]	Inception Date
Class I | Return Before Taxes	11.59%	15.74%	8.71%		Feb. 05, 2008
Class I | Return After Taxes on Distributions	10.58%	15.26%	8.31%		Feb. 05, 2008
Class I | Return After Taxes on Distributions and Sale of Fund Shares	7.33%	12.70%	6.96%		Feb. 05, 2008
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	15.45%	8.82%		Feb. 05, 2008
Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)	13.25%	15.01%	8.48%		Feb. 05, 2008

[1] From February 5, 2008.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

Series | Fidelity Advisor Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund:
FidelityAdvisor^® 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)

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%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

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:

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 www.advisor.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.advisor.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	0.42%	September 30, 2014
Year-to-Date Return	1.64%	June 30, 2015

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.

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.

For the periods ended
December 31, 2014

Series | Fidelity Advisor Series Growth & Income Fund | Class: Fidelity Advisor Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.22%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

Total annual operating expenses

^[1]

rr_ExpensesOverAssets

0.70%

1 year

rr_ExpenseExampleYear01

$ 72

3 years

rr_ExpenseExampleYear03

224

5 years

rr_ExpenseExampleYear05

390

10 years

rr_ExpenseExampleYear10

$ 871

2013

rr_AnnualReturn2013

32.36%

2014

rr_AnnualReturn2014

10.13%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.64%

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, 2014

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.42%

Series | Fidelity Advisor Series Growth & Income Fund | Return Before Taxes | Class: Fidelity Advisor Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Advisor Series Growth & Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

10.13%

Life of fund

^[2]

rr_AverageAnnualReturnSinceInception

20.44%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

Series | Fidelity Advisor Series Growth & Income Fund | Return After Taxes on Distributions | Class: Fidelity Advisor Series Growth & Income Fund

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

8.23%

Life of fund

^[2]

rr_AverageAnnualReturnSinceInception

18.91%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

Series | Fidelity Advisor Series Growth & Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Advisor Series Growth & Income Fund

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

6.30%

Life of fund

^[2]

rr_AverageAnnualReturnSinceInception

15.44%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of fund

^[2]

rr_AverageAnnualReturnSinceInception

22.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

Series | 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

Label

rr_AverageAnnualReturnLabel

Fidelity Series Growth & Income Fund Linked Index℠

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of fund

^[2]

rr_AverageAnnualReturnSinceInception

22.01%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

[2] From December 6, 2012

XML

Retail | 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
(fees paid directly from your investment)

Shareholder Fees	Retail Fidelity Growth Discovery Fund Class: Fidelity Growth Discovery Fund USD ($)
Shareholder fees (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	Retail Fidelity Growth Discovery Fund Class: Fidelity Growth Discovery Fund
Management fee (fluctuates based on the fund's performance relative to a securities market index)	0.55%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.22%
Total annual operating expenses	0.77%

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	Retail Fidelity Growth Discovery Fund Class: Fidelity Growth Discovery Fund USD ($)
1 year	$ 79
3 years	246
5 years	428
10 years	$ 954

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 51% 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 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 February 1, 2007, the fund operated under certain different investment policies and compared its performance to a different 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 www.fidelity.com for updated return 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	5.55%	June30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - Retail - Fidelity Growth Discovery Fund	Past 1 year	Past 5 years	Past 10 years
Class: Fidelity Growth Discovery Fund | Return Before Taxes	11.37%	16.75%	8.24%
Class: Fidelity Growth Discovery Fund | Return After Taxes on Distributions	11.34%	16.66%	8.14%
Class: Fidelity Growth Discovery Fund | Return After Taxes on Distributions and Sale of Fund Shares	6.46%	13.57%	6.72%
Russell 3000® Growth Index (reflects no deduction for fees, expenses, or taxes)	12.44%	15.89%	8.50%
Fidelity Growth Discovery Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)	12.44%	15.89%	8.98%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

Retail | 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)

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 22% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.00%

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:

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. Prior to December 1, 2007, the fund operated under certain different investment policies. 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 www.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and 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	1.33%	June 30, 2015

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.

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.

For the periods ended
December 31, 2014

Retail | Fidelity Mega Cap Stock Fund | Class: Fidelity Mega Cap Stock Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.22%

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

2005

rr_AnnualReturn2005

7.48%

2006

rr_AnnualReturn2006

12.84%

2007

rr_AnnualReturn2007

11.05%

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%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.33%

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%)

Retail | Fidelity Mega Cap Stock Fund | Return Before Taxes | Class: Fidelity Mega Cap Stock Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Mega Cap Stock Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.66%

Past 5 years

rr_AverageAnnualReturnYear05

15.78%

Past 10 years

rr_AverageAnnualReturnYear10

8.12%

Retail | Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions | Class: Fidelity Mega Cap Stock Fund

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

10.54%

Past 5 years

rr_AverageAnnualReturnYear05

15.28%

Past 10 years

rr_AverageAnnualReturnYear10

7.63%

Retail | Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Mega Cap Stock Fund

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

7.44%

Past 5 years

rr_AverageAnnualReturnYear05

12.73%

Past 10 years

rr_AverageAnnualReturnYear10

6.58%

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Past 5 years

rr_AverageAnnualReturnYear05

15.45%

Past 10 years

rr_AverageAnnualReturnYear10

7.67%

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Russell Top 200^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.25%

Past 5 years

rr_AverageAnnualReturnYear05

15.01%

Past 10 years

rr_AverageAnnualReturnYear10

7.33%

XML

Series | Fidelity Advisor Series Growth & Income Fund

Fund Summary

Fund:
FidelityAdvisor^® 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
(fees paid directly from your investment)

Shareholder Fees	Series Fidelity Advisor Series Growth & Income Fund Class: Fidelity Advisor Series Growth & Income Fund USD ($)
Shareholder fees (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		Series Fidelity Advisor Series Growth & Income Fund Class: Fidelity Advisor Series Growth & Income Fund
Management fee		0.45%
Distribution and/or Service (12b-1) fees		none
Other expenses		0.22%
Acquired fund fees and expenses		0.03%
Total annual operating expenses	[1]	0.70%

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	Series Fidelity Advisor Series Growth & Income Fund Class: Fidelity Advisor Series Growth & Income Fund USD ($)
1 year	$ 72
3 years	224
5 years	390
10 years	$ 871

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 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 www.advisor.fidelity.com for updated return 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	0.42%	September 30, 2014
Year-to-Date Return	1.64%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - Series - Fidelity Advisor Series Growth & Income Fund	Past 1 year	Life of fund	[1]	Inception Date
Class: Fidelity Advisor Series Growth & Income Fund | Return Before Taxes	10.13%	20.44%		Dec. 06, 2012
Class: Fidelity Advisor Series Growth & Income Fund | Return After Taxes on Distributions	8.23%	18.91%		Dec. 06, 2012
Class: Fidelity Advisor Series Growth & Income Fund | Return After Taxes on Distributions and Sale of Fund Shares	6.30%	15.44%		Dec. 06, 2012
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	22.45%		Dec. 06, 2012
Fidelity Series Growth & Income Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)	13.69%	22.01%		Dec. 06, 2012

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

[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, 2015

Z | 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 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.

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 22% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.00%

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:

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 the performance of the fund's shares over the past 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 is not an indication of future performance.

Visit www.advisor.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the the performance of the fund's shares over the past 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.advisor.fidelity.com

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 Year

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	4.93%	June 30, 2014
Lowest Quarter Return	1.34%	September 30, 2014
Year-to-Date Return	1.46%	June 30, 2015

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns
For the periods ended
December 31, 2014

Z | Fidelity Mega Cap Stock Fund | Class Z

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.09%

Total annual operating expenses

rr_ExpensesOverAssets

0.54%

1 year

rr_ExpenseExampleYear01

$ 55

3 years

rr_ExpenseExampleYear03

173

5 years

rr_ExpenseExampleYear05

302

10 years

rr_ExpenseExampleYear10

$ 677

2014

rr_AnnualReturn2014

11.75%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.46%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2014

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

4.93%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2014

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

1.34%

Label

rr_AverageAnnualReturnLabel

Class Z

Past 1 year

rr_AverageAnnualReturnYear01

11.75%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

15.92%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 13, 2013

Z | Fidelity Mega Cap Stock Fund | S&P 500® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

17.53%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 13, 2013

Z | Fidelity Mega Cap Stock Fund | Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Russell Top 200^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.25%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

17.64%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 13, 2013

[1] From August 13, 2013.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

Retail | 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)

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 51% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

51.00%

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:

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 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 February 1, 2007, the fund operated under certain different investment policies and compared its performance to a different 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 www.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and 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	16.40%	March 31, 2012
Lowest Quarter Return	-27.00%	December 31, 2008
Year-to-Date Return	5.55%	June30, 2015

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.

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.

For the periods ended
December 31, 2014

Retail | Fidelity Growth Discovery Fund | Class: Fidelity Growth Discovery Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

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

rr_ManagementFeesOverAssets

0.55%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.22%

Total annual operating expenses

rr_ExpensesOverAssets

0.77%

1 year

rr_ExpenseExampleYear01

$ 79

3 years

rr_ExpenseExampleYear03

246

5 years

rr_ExpenseExampleYear05

428

10 years

rr_ExpenseExampleYear10

$ 954

2005

rr_AnnualReturn2005

2.14%

2006

rr_AnnualReturn2006

13.94%

2007

rr_AnnualReturn2007

26.84%

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%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

5.55%

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%)

Retail | Fidelity Growth Discovery Fund | Return Before Taxes | Class: Fidelity Growth Discovery Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Growth Discovery Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.37%

Past 5 years

rr_AverageAnnualReturnYear05

16.75%

Past 10 years

rr_AverageAnnualReturnYear10

8.24%

Retail | Fidelity Growth Discovery Fund | Return After Taxes on Distributions | Class: Fidelity Growth Discovery Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Growth Discovery Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

11.34%

Past 5 years

rr_AverageAnnualReturnYear05

16.66%

Past 10 years

rr_AverageAnnualReturnYear10

8.14%

Retail | Fidelity Growth Discovery Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Growth Discovery Fund

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

6.46%

Past 5 years

rr_AverageAnnualReturnYear05

13.57%

Past 10 years

rr_AverageAnnualReturnYear10

6.72%

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Russell 3000^® Growth Index

Past 1 year

rr_AverageAnnualReturnYear01

12.44%

Past 5 years

rr_AverageAnnualReturnYear05

15.89%

Past 10 years

rr_AverageAnnualReturnYear10

8.50%

Retail | Fidelity Growth Discovery Fund | Fidelity Growth Discovery Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Fidelity Growth Discovery Fund Linked Index℠

Past 1 year

rr_AverageAnnualReturnYear01

12.44%

Past 5 years

rr_AverageAnnualReturnYear05

15.89%

Past 10 years

rr_AverageAnnualReturnYear10

8.98%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

F | Fidelity Series Growth & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Series Growth & Income Fund /F

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)

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 40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

40.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

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:

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 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 www.401k.com and log in for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.401k.com and log in for updated return information

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	9.87%	March 31, 2013
Lowest Quarter Return	0.46%	September 30, 2014
Year-to-Date Return	1.66%	June 30, 2015

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.

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.

For the periods ended
December 31, 2014

F | Fidelity Series Growth & Income Fund | Class F

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.02%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

Total annual operating expenses

^[1]

rr_ExpensesOverAssets

0.50%

1 year

rr_ExpenseExampleYear01

$ 51

3 years

rr_ExpenseExampleYear03

160

5 years

rr_ExpenseExampleYear05

280

10 years

rr_ExpenseExampleYear10

$ 628

2013

rr_AnnualReturn2013

32.58%

2014

rr_AnnualReturn2014

10.29%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.66%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2013

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.87%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2014

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.46%

F | Fidelity Series Growth & Income Fund | Return Before Taxes | Class F

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class F

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

10.29%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

20.41%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

F | Fidelity Series Growth & Income Fund | Return After Taxes on Distributions | Class F

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class F

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

8.72%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

18.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

F | Fidelity Series Growth & Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class F

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class F

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

6.37%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

15.40%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

F | Fidelity Series Growth & Income Fund | S&P 500® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

22.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

F | Fidelity Series Growth & Income Fund | Fidelity Series Growth & Income Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Fidelity Series Growth & Income Fund Linked Index℠

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Life of class

^[2]

rr_AverageAnnualReturnSinceInception

22.01%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 06, 2012

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

[2] 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, 2015

K | 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)

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 59% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

59.00%

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:

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 updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.401k.com and log in for updated return information

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	4.34%	June 30, 2015

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns
For the periods ended
December 31, 2014

K | Fidelity Fund | Class K

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.34%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.07%

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%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

4.34%

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%)

Label

rr_AverageAnnualReturnLabel

Class K

Past 1 year

rr_AverageAnnualReturnYear01

12.98%

Past 5 years

rr_AverageAnnualReturnYear05

13.84%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

6.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 09, 2008

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Past 5 years

rr_AverageAnnualReturnYear05

15.45%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

8.46%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 09, 2008

[1] From May 9, 2008.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Jun. 30, 2015
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. 28, 2015
Document Effective Date	dei_DocumentEffectiveDate	Aug. 29, 2015
Prospectus Date	rr_ProspectusDate	Aug. 29, 2015

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY HASTINGS STREET TRUST
Prospectus Date	rr_ProspectusDate	Aug. 29, 2015
Document Creation Date	dei_DocumentCreationDate	Aug. 28, 2015

XML

A T B C | Fidelity Mega Cap Stock Fund

Fund Summary

Fund/Class:
Fidelity^® Mega Cap Stock Fund/Fidelity Advisor^® Mega Cap Stock Fund A, T, B, C

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.

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 (Click Here) of the prospectus.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees - A T B C - Fidelity Mega Cap Stock Fund	Class A		Class T		Class B		Class C
Maximum sales charge (load) on purchases (as a % of offering price)	5.75%		3.50%		none		none
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	none	[1]	none	[1]	5.00%	[2]	1.00%	[3]

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

Annual Operating Expenses - A T B C - Fidelity Mega Cap Stock Fund	Class A	Class T	Class B	Class C
Management fee	0.45%	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) fees	0.25%	0.50%	1.00%	1.00%
Other expenses	0.35%	0.26%	0.28%	0.25%
Total annual operating expenses	1.05%	1.21%	1.73%	1.70%

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 - A T B C - Fidelity Mega Cap Stock Fund - USD ($)	Class A	Class T	Class B	Class C
1 year	$ 676	$ 469	$ 676	$ 273
3 years	890	721	845	536
5 years	1,121	992	1,139	923
10 years	$ 1,784	$ 1,765	$ 1,777	$ 2,009

Hold Shares

Expense Example, No Redemption - A T B C - Fidelity Mega Cap Stock Fund - USD ($)	Class A	Class T	Class B	Class C
1 year	$ 676	$ 469	$ 176	$ 173
3 years	890	721	545	536
5 years	1,121	992	939	923
10 years	$ 1,784	$ 1,765	$ 1,777	$ 2,009

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 22% 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.advisor.fidelity.com for updated return information.

Year-by-Year Returns

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.

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	1.16%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - A T B C - Fidelity Mega Cap Stock Fund	Past 1 year	Past 5 years	Life of class	[1]	Inception Date
Class A | Return Before Taxes	4.83%	14.08%	7.48%		Feb. 05, 2008
Class A | Return After Taxes on Distributions	3.83%	13.63%	7.11%		Feb. 05, 2008
Class A | Return After Taxes on Distributions and Sale of Fund Shares	3.49%	11.30%	5.94%		Feb. 05, 2008
Class T | Return Before Taxes	7.16%	14.32%	7.58%		Feb. 05, 2008
Class B | Return Before Taxes	5.48%	14.30%	7.58%		Feb. 05, 2008
Class C | Return Before Taxes	9.52%	14.58%	7.61%		Feb. 05, 2008
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	15.45%	8.82%		Feb. 05, 2008
Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)	13.25%	15.01%	8.48%		Feb. 05, 2008

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

[2] Declines over 6 years from 5.00% to 0%.

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

[1] From February 5, 2008.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

Retail | 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)

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 59% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

59.00%

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:

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 updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index 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	4.29%	June 30, 2015

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.

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.

For the periods ended
December 31, 2014

Retail | Fidelity Fund | Class: Fidelity Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.34%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.18%

Total annual operating expenses

rr_ExpensesOverAssets

0.52%

1 year

rr_ExpenseExampleYear01

$ 53

3 years

rr_ExpenseExampleYear03

167

5 years

rr_ExpenseExampleYear05

291

10 years

rr_ExpenseExampleYear10

$ 653

2005

rr_AnnualReturn2005

7.52%

2006

rr_AnnualReturn2006

13.67%

2007

rr_AnnualReturn2007

16.81%

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%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

4.29%

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%)

Retail | Fidelity Fund | Return Before Taxes | Class: Fidelity Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

12.85%

Past 5 years

rr_AverageAnnualReturnYear05

13.68%

Past 10 years

rr_AverageAnnualReturnYear10

7.44%

Retail | Fidelity Fund | Return After Taxes on Distributions | Class: Fidelity Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

9.60%

Past 5 years

rr_AverageAnnualReturnYear05

12.48%

Past 10 years

rr_AverageAnnualReturnYear10

6.67%

Retail | Fidelity Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Fund

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

9.27%

Past 5 years

rr_AverageAnnualReturnYear05

10.84%

Past 10 years

rr_AverageAnnualReturnYear10

5.99%

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

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Past 5 years

rr_AverageAnnualReturnYear05

15.45%

Past 10 years

rr_AverageAnnualReturnYear10

7.67%

XML

F | Fidelity Series Growth & Income Fund

Fund Summary

Fund/Class:
Fidelity^® Series Growth & Income Fund /F

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
(fees paid directly from your investment)

Shareholder Fees	F Fidelity Series Growth & Income Fund Class F USD ($)
Shareholder fees (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		F Fidelity Series Growth & Income Fund Class F
Management fee		0.45%
Distribution and/or Service (12b-1) fees		none
Other expenses		0.02%
Acquired fund fees and expenses		0.03%
Total annual operating expenses	[1]	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:

Expense Example	F Fidelity Series Growth & Income Fund Class F 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 40% 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 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 www.401k.com and log in for updated return information.

Year-by-Year Returns
Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	9.87%	March 31, 2013
Lowest Quarter Return	0.46%	September 30, 2014
Year-to-Date Return	1.66%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - F - Fidelity Series Growth & Income Fund	Past 1 year	Life of class	[1]	Inception Date
Class F | Return Before Taxes	10.29%	20.41%		Dec. 06, 2012
Class F | Return After Taxes on Distributions	8.72%	18.87%		Dec. 06, 2012
Class F | Return After Taxes on Distributions and Sale of Fund Shares	6.37%	15.40%		Dec. 06, 2012
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	22.45%		Dec. 06, 2012
Fidelity Series Growth & Income Fund Linked Index℠ (reflects no deduction for fees, expenses, or taxes)	13.69%	22.01%		Dec. 06, 2012

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.

[1] From December 6, 2012.

XML

K | 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
(fees paid directly from your investment)

Shareholder Fees	K Fidelity Fund Class K USD ($)
Shareholder fees (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	K Fidelity Fund Class K
Management fee	0.34%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.07%
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:

Expense Example	K 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 59% 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 updated return 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	4.34%	June 30, 2015

Average Annual Returns
For the periods ended
December 31, 2014

Average Annual Total Returns - K - Fidelity Fund	Past 1 year	Past 5 years	Life of class	[1]	Inception Date
Class K	12.98%	13.84%	6.66%		May 09, 2008
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	15.45%	8.46%		May 09, 2008

[1] From May 9, 2008.

XML

Retail | 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
(fees paid directly from your investment)

Shareholder Fees	Retail Fidelity Mega Cap Stock Fund Class: Fidelity Mega Cap Stock Fund USD ($)
Shareholder fees (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	Retail Fidelity Mega Cap Stock Fund Class: Fidelity Mega Cap Stock Fund
Management fee	0.45%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.22%
Total annual operating expenses	0.67%

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	Retail Fidelity Mega Cap Stock Fund Class: Fidelity Mega Cap Stock Fund USD ($)
1 year	$ 68
3 years	214
5 years	373
10 years	$ 835

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 22% 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. Prior to December 1, 2007, the fund operated under certain different investment policies. 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 www.fidelity.com for updated return 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	1.33%	June 30, 2015

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.

For the periods ended
December 31, 2014

Average Annual Total Returns - Retail - Fidelity Mega Cap Stock Fund	Past 1 year	Past 5 years	Past 10 years
Class: Fidelity Mega Cap Stock Fund | Return Before Taxes	11.66%	15.78%	8.12%
Class: Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions	10.54%	15.28%	7.63%
Class: Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions and Sale of Fund Shares	7.44%	12.73%	6.58%
S&P 500® Index (reflects no deduction for fees, expenses, or taxes)	13.69%	15.45%	7.67%
Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)	13.25%	15.01%	7.33%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY HASTINGS STREET TRUST

Prospectus Date

rr_ProspectusDate

Aug. 29, 2015

I | 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 I

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)

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 22% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.00%

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:

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.advisor.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.advisor.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	18.36%	June 30, 2009
Lowest Quarter Return	-13.08%	September 30, 2011
Year-to-Date Return	1.33%	June 30, 2015

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.

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.

For the periods ended
December 31, 2014

I | Fidelity Mega Cap Stock Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.45%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual operating expenses

rr_ExpensesOverAssets

0.69%

1 year

rr_ExpenseExampleYear01

$ 70

3 years

rr_ExpenseExampleYear03

221

5 years

rr_ExpenseExampleYear05

384

10 years

rr_ExpenseExampleYear10

$ 859

2009

rr_AnnualReturn2009

28.55%

2010

rr_AnnualReturn2010

14.35%

2011

rr_AnnualReturn2011

2.28%

2012

rr_AnnualReturn2012

19.48%

2013

rr_AnnualReturn2013

33.18%

2014

rr_AnnualReturn2014

11.59%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2015

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.33%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.36%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(13.08%)

I | Fidelity Mega Cap Stock Fund | Return Before Taxes | Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class I

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.59%

Past 5 years

rr_AverageAnnualReturnYear05

15.74%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

8.71%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

I | Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions | Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class I

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

10.58%

Past 5 years

rr_AverageAnnualReturnYear05

15.26%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

8.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

I | Fidelity Mega Cap Stock Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class I

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

7.33%

Past 5 years

rr_AverageAnnualReturnYear05

12.70%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

6.96%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

I | Fidelity Mega Cap Stock Fund | S&P 500® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P 500^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.69%

Past 5 years

rr_AverageAnnualReturnYear05

15.45%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

8.82%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

I | Fidelity Mega Cap Stock Fund | Russell Top 200® Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Russell Top 200^® Index

Past 1 year

rr_AverageAnnualReturnYear01

13.25%

Past 5 years

rr_AverageAnnualReturnYear05

15.01%

Life of class

^[1]

rr_AverageAnnualReturnSinceInception

8.48%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 05, 2008

[1] From February 5, 2008.