Document and Entity Information
v0.0.0.0
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Mar. 01, 2012
Registrant Name dei_EntityRegistrantName FENIMORE ASSET MANAGEMENT TRUST
Central Index Key dei_EntityCentralIndexKey 0000797136
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Feb. 29, 2012
Document Effective Date dei_DocumentEffectiveDate Mar. 01, 2012
Prospectus Date rr_ProspectusDate Mar. 01, 2012

Risk_Return Summary - (FAM Small Cap Fund) (Investor)
v0.0.0.0
Investor | FAM Small Cap Fund
Shareholder Fees -
Investor
FAM Small Cap Fund
Investor Class
Maximum sales charge (load) on purchase none
Maximum deferred sales charge (load) none
Redemption fee none
Annual Fund Operating Expenses -
Investor
FAM Small Cap Fund
Investor Class
Management Fees 1.00%
Distribution and Service (12b-1) Fees none
Other expenses [1] 1.50%
Total annual fund operating expenses 2.50%
Fee waiver and/or expense reimbursement [2] 1.00%
Total Annual Fund Operating Expenses after Waiver and/or Reimbursement [2] 1.50%
[1] Based on estimated amounts for the Fund's initial fiscal year of operations.
[2] Fenimore Asset Management (FAM) has entered into a contractual agreement with FAM Small Cap Fund to limit the total operating expenses of the Fund's Investor Class shares to 1.50% of its average daily net assets through May 1, 2015. This expense limitation agreement may only be amended by the Fund's Board of Trustees.
Expense Example - (USD $)
1 YEAR
3 YEARS
Investor FAM Small Cap Fund Investor Class
153 474

Risk_Return Detail Data - (FAM Small Cap Fund) (Investor)
v0.0.0.0
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName FENIMORE ASSET MANAGEMENT TRUST
Prospectus Date rr_ProspectusDate Mar. 01, 2012
Investor | FAM Small Cap Fund | Investor Class
 
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) on purchase rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee rr_RedemptionFeeOverRedemption none
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 1.50% [1]
Total annual fund operating expenses rr_ExpensesOverAssets 2.50%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets 1.00% [2]
Total Annual Fund Operating Expenses after Waiver and/or Reimbursement rr_NetExpensesOverAssets 1.50% [2]
1 YEAR rr_ExpenseExampleYear01 $ 153
3 YEARS rr_ExpenseExampleYear03 $ 474
Investor | FAM Small Cap Fund
 
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Objective [Heading] rr_ObjectiveHeading
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Expense [Heading] rr_ExpenseHeading
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption
Operating Expenses Caption [Text] rr_OperatingExpensesCaption
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination May 1, 2015
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Based on estimated amounts for the Fund's initial fiscal year of operations
Expense Example [Heading] rr_ExpenseExampleHeading
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption
Strategy [Heading] rr_StrategyHeading
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Risk [Heading] rr_RiskHeading
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
Risk Lose Money [Text] rr_RiskLoseMoney the value of your investment will go up and down, which means that you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess The inception date for the Fund is March 1, 2012.  The Fund's performance will then be compared to the Russell 2000 Index.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.famfunds.com
[1] Based on estimated amounts for the Fund's initial fiscal year of operations.
[2] Fenimore Asset Management (FAM) has entered into a contractual agreement with FAM Small Cap Fund to limit the total operating expenses of the Fund's Investor Class shares to 1.50% of its average daily net assets through May 1, 2015. This expense limitation agreement may only be amended by the Fund's Board of Trustees.

Risk_Return Summary - (FAM Small Cap Fund) (Advisor)
v0.0.0.0
Advisor | FAM Small Cap Fund
Shareholder Fees -
Advisor
FAM Small Cap Fund
Advisor Class
Maximum sales charge (load) on purchase none
Maximum deferred sales charge (load) none
Redemption fee 1.00%
Annual Fund Operating Expenses -
Advisor
FAM Small Cap Fund
Advisor Class
Management Fees 1.00%
Distribution and Service (12b-1) Fees 1.00%
Other expenses [1] 1.50%
Total annual fund operating expenses 3.50%
Fee waiver and/or expense reimbursement [2] 1.00%
Total Annual Fund Operating Expenses after Waiver and/or Reimbursement [2] 2.50%
[1] Based on estimated amounts for the Fund's initial fiscal year of operations.
[2] Fenimore Asset Management (FAM) has entered into a contractual agreement with FAM Small Cap Fund to limit the total operating expenses of the Fund's Advisor Class shares to 2.50% of its average daily net assets through May 1, 2015. This expense limitation agreement may only be amended by the Fund's Board of Trustees.
This Example is intended to help you compare the cost of investing in other mutual funds.  The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods.  The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example - (USD $)
1 YEAR
3 YEARS
Advisor FAM Small Cap Fund Advisor Class
253 779

Risk_Return Detail Data - (FAM Small Cap Fund) (Advisor)
v0.0.0.0
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName FENIMORE ASSET MANAGEMENT TRUST
Prospectus Date rr_ProspectusDate Mar. 01, 2012
Advisor | FAM Small Cap Fund | Advisor Class
 
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) on purchase rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee rr_RedemptionFeeOverRedemption 1.00%
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 1.50% [1]
Total annual fund operating expenses rr_ExpensesOverAssets 3.50%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets 1.00% [2]
Total Annual Fund Operating Expenses after Waiver and/or Reimbursement rr_NetExpensesOverAssets 2.50% [2]
1 YEAR rr_ExpenseExampleYear01 $ 253
3 YEARS rr_ExpenseExampleYear03 $ 779
Advisor | FAM Small Cap Fund
 
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Objective [Heading] rr_ObjectiveHeading
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Expense [Heading] rr_ExpenseHeading
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption
Operating Expenses Caption [Text] rr_OperatingExpensesCaption
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination May 1, 2015
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Based on estimated amounts for the Fund's initial fiscal year of operations
Expense Example [Heading] rr_ExpenseExampleHeading
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in other mutual funds.  The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods.  The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption
Strategy [Heading] rr_StrategyHeading
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Risk [Heading] rr_RiskHeading
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
Risk Lose Money [Text] rr_RiskLoseMoney the value of your investment will go up and down, which means that you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Non-diversification Risk – the Fund is classified as a " non-diversified" fund which means that the Fund may own larger positions in a smaller number of securities.   A fund that is less diversified, such as the Fund, may be more susceptible to adverse economic, political, or regulatory developments affecting a single issuer than a fund that is more broadly diversified.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.famfunds.com
[1] Based on estimated amounts for the Fund's initial fiscal year of operations.
[2] Fenimore Asset Management (FAM) has entered into a contractual agreement with FAM Small Cap Fund to limit the total operating expenses of the Fund's Advisor Class shares to 2.50% of its average daily net assets through May 1, 2015. This expense limitation agreement may only be amended by the Fund's Board of Trustees.

Risk_Return Detail Data
v0.0.0.0
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Prospectus Date rr_ProspectusDate Mar. 01, 2012