XML 9 R46.htm IDEA: XBRL DOCUMENT v2.4.0.6
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Oct. 31, 2011
Registrant Name dei_EntityRegistrantName Fidelity Newbury Street Trust
Central Index Key dei_EntityCentralIndexKey 0000704207
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Dec. 29, 2011
Document Effective Date dei_DocumentEffectiveDate Dec. 30, 2011
Prospectus Date rr_ProspectusDate Dec. 30, 2011
Prime Fund | Cap Reserves
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Prime Fund/Capital Reserves
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to obtain as high a level of current income as is consistent with the preservation of capital and liquidity.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Investing in U.S. dollar-denominated money market securities of domestic and foreign issuers rated in the highest category by at least two nationally recognized rating services, U.S. Government securities, and repurchase agreements.
  • Potentially entering into reverse repurchase agreements.
  • Investing more than 25% of total assets in the financial services industries.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration
  • Investing more than 25% of total assets in the financial services industries.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries.
  • Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.

Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return1.28%March 31, 2001
Lowest Quarter Return0.00%September 30, 2009
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Prime Fund | Daily Money
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Prime Fund/Daily Money
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to obtain as high a level of current income as is consistent with the preservation of capital and liquidity.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:
Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Investing in U.S. dollar-denominated money market securities of domestic and foreign issuers rated in the highest category by at least two nationally recognized rating services, U.S. Government securities, and repurchase agreements.
  • Potentially entering into reverse repurchase agreements.
  • Investing more than 25% of total assets in the financial services industries.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration
  • Investing more than 25% of total assets in the financial services industries.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries.
  • Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return1.34%March 31, 2001
Lowest Quarter Return0.00%December 31, 2010
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Prime Fund | Prime Fund - Capital Reserves Class | Cap Reserves
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other expenses rr_OtherExpensesOverAssets 0.24%
Total annual operating expenses rr_ExpensesOverAssets 0.99%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 101
3 years rr_ExpenseExampleYear03 315
5 years rr_ExpenseExampleYear05 547
10 years rr_ExpenseExampleYear10 1,213
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 3.43%
2002 rr_AnnualReturn2002 1.00%
2003 rr_AnnualReturn2003 0.31%
2004 rr_AnnualReturn2004 0.51%
2005 rr_AnnualReturn2005 2.40%
2006 rr_AnnualReturn2006 4.23%
2007 rr_AnnualReturn2007 4.52%
2008 rr_AnnualReturn2008 2.25%
2009 rr_AnnualReturn2009 0.16%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.28%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2001
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2009
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Capital Reserves Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 2.22%
Past 10 years rr_AverageAnnualReturnYear10 1.87%
Prime Fund | Prime Fund - Daily Money Class | Daily Money
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.24%
Total annual operating expenses rr_ExpensesOverAssets 0.74%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 76
3 years rr_ExpenseExampleYear03 237
5 years rr_ExpenseExampleYear05 411
10 years rr_ExpenseExampleYear10 918
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 3.69%
2002 rr_AnnualReturn2002 1.25%
2003 rr_AnnualReturn2003 0.56%
2004 rr_AnnualReturn2004 0.76%
2005 rr_AnnualReturn2005 2.65%
2006 rr_AnnualReturn2006 4.49%
2007 rr_AnnualReturn2007 4.78%
2008 rr_AnnualReturn2008 2.51%
2009 rr_AnnualReturn2009 0.28%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.34%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2001
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2010
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Daily Money Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 2.39%
Past 10 years rr_AverageAnnualReturnYear10 2.08%
Tax-Exempt Fund | Cap Reserves
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Tax-Exempt Fund/Capital Reserves
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to provide as high a level of current income, exempt from federal income taxes, as is consistent with liquidity and stability of principal.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing in municipal money market securities.
  • Normally investing at least 80% of assets in municipal securities whose interest is exempt from federal income tax.
  • Normally not investing in municipal securities whose interest is subject to the federal alternative minimum tax.
  • Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Municipal Market Volatility. The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities.
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.72%June 30, 2007
Lowest Quarter Return0.00%March 31, 2010
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Tax-Exempt Fund | Daily Money
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Tax-Exempt Fund/Daily Money
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to provide as high a level of current income, exempt from federal income taxes, as is consistent with liquidity and stability of principal.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing in municipal money market securities.
  • Normally investing at least 80% of assets in municipal securities whose interest is exempt from federal income tax.
  • Normally not investing in municipal securities whose interest is subject to the federal alternative minimum tax.
  • Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Municipal Market Volatility. The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities.
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.78%June 30, 2007
Lowest Quarter Return0.00%March 31, 2010
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Tax-Exempt Fund | Retail
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Tax-Exempt Fund/Fidelity® Tax-Free Money Market Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to provide as high a level of current income, exempt from federal income taxes, as is consistent with liquidity and stability of principal.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:
Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing in municipal money market securities.
  • Normally investing at least 80% of assets in municipal securities whose interest is exempt from federal income tax.
  • Normally not investing in municipal securities whose interest is subject to the federal alternative minimum tax.
  • Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Municipal Market Volatility. The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities.
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. Past performance 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.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.84% June 30, 2007
Lowest Quarter Return0.00%March 31, 2010
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Tax-Exempt Fund | Tax-Exempt Fund - Capital Reserves Class | Cap Reserves
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other expenses rr_OtherExpensesOverAssets 0.22%
Total annual operating expenses rr_ExpensesOverAssets 0.97%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 99
3 years rr_ExpenseExampleYear03 309
5 years rr_ExpenseExampleYear05 536
10 years rr_ExpenseExampleYear10 1,190
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 1.97%
2002 rr_AnnualReturn2002 0.66%
2003 rr_AnnualReturn2003 0.23%
2004 rr_AnnualReturn2004 0.33%
2005 rr_AnnualReturn2005 1.55%
2006 rr_AnnualReturn2006 2.57%
2007 rr_AnnualReturn2007 2.78%
2008 rr_AnnualReturn2008 1.20%
2009 rr_AnnualReturn2009 0.01%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.72%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2007
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Capital Reserves Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 1.31%
Past 10 years rr_AverageAnnualReturnYear10 1.13%
Tax-Exempt Fund | Tax-Exempt Fund - Daily Money Class | Daily Money
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.22%
Total annual operating expenses rr_ExpensesOverAssets 0.72%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 74
3 years rr_ExpenseExampleYear03 230
5 years rr_ExpenseExampleYear05 401
10 years rr_ExpenseExampleYear10 894
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 2.23%
2002 rr_AnnualReturn2002 0.93%
2003 rr_AnnualReturn2003 0.45%
2004 rr_AnnualReturn2004 0.57%
2005 rr_AnnualReturn2005 1.81%
2006 rr_AnnualReturn2006 2.83%
2007 rr_AnnualReturn2007 3.04%
2008 rr_AnnualReturn2008 1.45%
2009 rr_AnnualReturn2009 0.01%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.78%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2007
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Daily Money Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 1.46%
Past 10 years rr_AverageAnnualReturnYear10 1.33%
Tax-Exempt Fund | Tax-Free Money Market Fund | Retail
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.22%
Total annual operating expenses rr_ExpensesOverAssets 0.47%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 48
3 years rr_ExpenseExampleYear03 151
5 years rr_ExpenseExampleYear05 263
10 years rr_ExpenseExampleYear10 591
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 1.16%
2003 rr_AnnualReturn2003 0.71%
2004 rr_AnnualReturn2004 0.82%
2005 rr_AnnualReturn2005 2.06%
2006 rr_AnnualReturn2006 3.08%
2007 rr_AnnualReturn2007 3.30%
2008 rr_AnnualReturn2008 1.70%
2009 rr_AnnualReturn2009 0.09%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.84%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2007
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Fidelity® Tax-Free Money Market Fund
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 1.63%
Life of class rr_AverageAnnualReturnSinceInception 1.46% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 19, 2001
Treasury Fund | Cap Reserves
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Treasury Fund/Capital Reserves
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to obtain as high a level of current income as is consistent with the preservation of capital and liquidity.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy, hold, or sell shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing at least 80% of assets in U.S. Treasury securities and repurchase agreements for those securities.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.

Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return1.19%March 31, 2001
Lowest Quarter Return0.00%March 31, 2009
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Treasury Fund | Daily Money
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Treasury Fund/Daily Money
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to obtain as high a level of current income as is consistent with the preservation of capital and liquidity.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy, hold, or sell shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing at least 80% of assets in U.S. Treasury securities and repurchase agreements for those securities.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return1.25% March 31, 2001
Lowest Quarter Return0.00%March 30, 2010
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Returns

For the periods ended
December 31, 2010
Treasury Fund | Adv B Adv C
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Treasury Fund/Advisor B (Class B), Advisor C (Class C)
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to obtain as high a level of current income as is consistent with the preservation of capital and liquidity.
Fee Table fnst704207_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy, hold, or sell shares of the fund.
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated and if you hold your shares:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Sell All Shares
Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
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 U.S. Treasury securities and repurchase agreements for those securities.
  • Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, and diversification of investments.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease.
  • Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fnst704207_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. 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 changes in the performance of the fund's shares from year to year.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
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 B:
Returns
Quarter ended
Highest Quarter Return1.07% March 31, 2001
Lowest Quarter Return0.00%March 31, 2009
Year-to-Date Return0.01%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges.
For the periods ended
December 31, 2010
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.
Treasury Fund | Treasury Fund - Capital Reserves Class | Cap Reserves
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other expenses rr_OtherExpensesOverAssets 0.23%
Total annual operating expenses rr_ExpensesOverAssets 0.98%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 100
3 years rr_ExpenseExampleYear03 312
5 years rr_ExpenseExampleYear05 542
10 years rr_ExpenseExampleYear10 1,201
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 3.22%
2002 rr_AnnualReturn2002 0.88%
2003 rr_AnnualReturn2003 0.23%
2004 rr_AnnualReturn2004 0.41%
2005 rr_AnnualReturn2005 2.27%
2006 rr_AnnualReturn2006 4.11%
2007 rr_AnnualReturn2007 4.08%
2008 rr_AnnualReturn2008 1.04%
2009 rr_AnnualReturn2009 0.01%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.19%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2001
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2009
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Capital Reserves Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 1.83%
Past 10 years rr_AverageAnnualReturnYear10 1.61%
Treasury Fund | Treasury Fund - Daily Money Class | Daily Money
  
Shareholder fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.23%
Total annual operating expenses rr_ExpensesOverAssets 0.73%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 75
3 years rr_ExpenseExampleYear03 233
5 years rr_ExpenseExampleYear05 406
10 years rr_ExpenseExampleYear10 906
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 3.47%
2002 rr_AnnualReturn2002 1.13%
2003 rr_AnnualReturn2003 0.48%
2004 rr_AnnualReturn2004 0.66%
2005 rr_AnnualReturn2005 2.52%
2006 rr_AnnualReturn2006 4.38%
2007 rr_AnnualReturn2007 4.34%
2008 rr_AnnualReturn2008 1.24%
2009 rr_AnnualReturn2009 0.01%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.25%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2001
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 30, 2010
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Daily Money Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 1.98%
Past 10 years rr_AverageAnnualReturnYear10 1.81%
Treasury Fund | Treasury Fund - Advisor B Class | Adv B Adv C
  
Shareholder fees rr_ShareholderFeesAbstract  
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 5.00% [2]
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock Maximum contingent deferred sales charge (CDSC) declines over 6 years from 5.00% to 0%.
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 0.24%
Total annual operating expenses rr_ExpensesOverAssets 1.49%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 652
3 years rr_ExpenseExampleYear03 771
5 years rr_ExpenseExampleYear05 1,013
10 years rr_ExpenseExampleYear10 1,477
Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
1 year rr_ExpenseExampleNoRedemptionYear01 152
3 years rr_ExpenseExampleNoRedemptionYear03 471
5 years rr_ExpenseExampleNoRedemptionYear05 813
10 years rr_ExpenseExampleNoRedemptionYear10 1,477
Annual Total Returns rr_BarChartTableAbstract  
2001 rr_AnnualReturn2001 2.70%
2002 rr_AnnualReturn2002 0.39%
2003 rr_AnnualReturn2003 0.11%
2004 rr_AnnualReturn2004 0.19%
2005 rr_AnnualReturn2005 1.76%
2006 rr_AnnualReturn2006 3.59%
2007 rr_AnnualReturn2007 3.56%
2008 rr_AnnualReturn2008 0.68%
2009 rr_AnnualReturn2009 0.01%
2010 rr_AnnualReturn2010 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.07%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2001
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2009
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Class B
Past 1 year rr_AverageAnnualReturnYear01 (4.99%)
Past 5 years rr_AverageAnnualReturnYear05 1.18%
Past 10 years rr_AverageAnnualReturnYear10 1.35%
Treasury Fund | Treasury Fund - Advisor C Class | Adv B Adv C
  
Shareholder fees rr_ShareholderFeesAbstract  
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00% [3]
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock On Class C shares redeemed less than one year after purchase.
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.25%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 0.23%
Total annual operating expenses rr_ExpensesOverAssets 1.48%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 251
3 years rr_ExpenseExampleYear03 468
5 years rr_ExpenseExampleYear05 808
10 years rr_ExpenseExampleYear10 1,768
Expense Example, No Redemption rr_ExpenseExampleNoRedemptionAbstract  
1 year rr_ExpenseExampleNoRedemptionYear01 151
3 years rr_ExpenseExampleNoRedemptionYear03 468
5 years rr_ExpenseExampleNoRedemptionYear05 808
10 years rr_ExpenseExampleNoRedemptionYear10 1,768
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Class C
Past 1 year rr_AverageAnnualReturnYear01 (0.99%)
Past 5 years rr_AverageAnnualReturnYear05 1.56%
Past 10 years rr_AverageAnnualReturnYear10 1.29%
[1] From June 19, 2001.
[2] Maximum contingent deferred sales charge (CDSC) declines over 6 years from 5.00% to 0%.
[3] On Class C shares redeemed less than one year after purchase.