Document and Entity Information
v2.2.0.25
LabelElementValue
Risk/Return:rr_RiskReturnAbstract 
Document Typedei_DocumentType485BPOS
Document Period End Datedei_DocumentPeriodEndDateDec. 31, 2010
Registrant Namedei_EntityRegistrantNameFENIMORE ASSET MANAGEMENT TRUST
Central Index Keydei_EntityCentralIndexKey0000797136
Amendment Flagdei_AmendmentFlagfalse
Document Creation Datedei_DocumentCreationDateApr. 29, 2011
Document Effective Datedei_DocumentEffectiveDateMay 01, 2011
Prospectus Daterr_ProspectusDateMay 01, 2011

Risk_Return Summary - (FAM Value Fund) (Investor Share Calss)
v2.2.0.25
Investor Share Class | FAM Value Fund
Shareholder Fees -
Investor Share Class
FAM Value Fund
Investor Class
Maximum sales charge (load) on purchasenone
Maximum deferred sales charge (load)none
Redemption feenone
Annual Fund Operating Expenses -
Investor Share Class
FAM Value Fund
Investor Class
Management Fees1.00%
Distribution and Service (12b-1) Feesnone
Other expenses0.23%
Acquired Fund Fees and Expenses0.01%
Total Annual Fund Operating Expenses1.24%
Expense Example - (USD $)
1 YEAR
3 YEARS
5 YEARS
10 YEARS
Investor Share Class FAM Value Fund Investor Class
1263936811,500
Bar Chart
Average Annual Total Returns - Investor Share Class FAM Value Fund
1 YEAR
5 YEARS
10 YEARS
Investor Class
17.02%1.92%6.33%
Investor Class Return after taxes on distributions
16.72%1.32%5.73%
Investor Class Return after taxes on distributions and sale of fund share
11.37%1.48%5.37%
Russell 2000 Index
26.85%4.47%6.33%

Risk_Return Detail Data - (FAM Value Fund) (Investor Share Class)
v2.2.0.25
LabelElementValue
Risk/Return:rr_RiskReturnAbstract 
Registrant Namedei_EntityRegistrantNameFENIMORE ASSET MANAGEMENT TRUST
Prospectus Daterr_ProspectusDateMay 01, 2011
Investor Share Class | FAM Value Fund | Investor Class
 
Risk/Return:rr_RiskReturnAbstract 
Maximum sales charge (load) on purchaserr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricenone
Maximum deferred sales charge (load)rr_MaximumDeferredSalesChargeOverOthernone
Redemption feerr_RedemptionFeeOverRedemptionnone
Management Feesrr_ManagementFeesOverAssets1.00%
Distribution and Service (12b-1) Feesrr_DistributionAndService12b1FeesOverAssetsnone
Other expensesrr_OtherExpensesOverAssets0.23%
Acquired Fund Fees and Expensesrr_AcquiredFundFeesAndExpensesOverAssets0.01%
Total Annual Fund Operating Expensesrr_ExpensesOverAssets1.24%
1 YEARrr_ExpenseExampleYear01 126
3 YEARSrr_ExpenseExampleYear03393
5 YEARSrr_ExpenseExampleYear05681
10 YEARSrr_ExpenseExampleYear10 1,500
Annual Return 2001rr_AnnualReturn200115.07%
Annual Return 2002rr_AnnualReturn2002(5.33%)
Annual Return 2003rr_AnnualReturn200324.98%
Annual Return 2004rr_AnnualReturn200416.86%
Annual Return 2005rr_AnnualReturn20055.56%
Annual Return 2006rr_AnnualReturn20068.73%
Annual Return 2007rr_AnnualReturn2007(0.79%)
Annual Return 2008rr_AnnualReturn2008(28.68%)
Annual Return 2009rr_AnnualReturn200922.18%
Annual Return 2010rr_AnnualReturn201017.02%
Highest Quarterly Return, Labelrr_HighestQuarterlyReturnLabelBest Quarter
Highest Quarterly Return, Daterr_BarChartHighestQuarterlyReturnDateMar. 31, 2003
Highest Quarterly Returnrr_BarChartHighestQuarterlyReturn13.18%
Lowest Quarterly Return, Labelrr_LowestQuarterlyReturnLabelWorst Quarter
Lowest Quarterly Return, Daterr_BarChartLowestQuarterlyReturnDateDec. 31, 2008
Lowest Quarterly Returnrr_BarChartLowestQuarterlyReturn(20.68%)
1 YEARrr_AverageAnnualReturnYear0117.02%
5 YEARSrr_AverageAnnualReturnYear051.92%
10 YEARSrr_AverageAnnualReturnYear106.33%
Investor Share Class | FAM Value Fund | Investor Class | Return after taxes on distributions
 
Risk/Return:rr_RiskReturnAbstract 
1 YEARrr_AverageAnnualReturnYear0116.72%
5 YEARSrr_AverageAnnualReturnYear051.32%
10 YEARSrr_AverageAnnualReturnYear105.73%
Investor Share Class | FAM Value Fund | Investor Class | Return after taxes on distributions and sale of fund share
 
Risk/Return:rr_RiskReturnAbstract 
1 YEARrr_AverageAnnualReturnYear0111.37%
5 YEARSrr_AverageAnnualReturnYear051.48%
10 YEARSrr_AverageAnnualReturnYear105.37%
Investor Share Class | FAM Value 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
Portfolio Turnover [Heading]rr_PortfolioTurnoverHeading
Portfolio Turnover [Text Block]rr_PortfolioTurnoverTextBlock
Portfolio Turnover, Raterr_PortfolioTurnoverRate5.08%
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_RiskLoseMoneythe value of your investment will go up and down, which means that you could lose money.
Bar Chart and Performance Table [Heading]rr_BarChartAndPerformanceTableHeading
Performance Narrative [Text Block]rr_PerformanceNarrativeTextBlock
Performance Information Illustrates Variability of Returns [Text]rr_PerformanceInformationIllustratesVariabilityOfReturnsThe bar chart shows changes in the Investor Class shares performance since 2001. The table shows how Investor Class shares' average annual returns  (before and after taxes) for the one year; five year and ten year periods compared to those of the Russell 2000 Index.
Performance Availability Website Address [Text]rr_PerformanceAvailabilityWebSiteAddresswww.famfunds.com
Performance Past Does Not Indicate Future [Text]rr_PerformancePastDoesNotIndicateFutureThe Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]rr_BarChartHeading
Bar Chart Closing [Text Block]rr_BarChartClosingTextBlock
Performance Table Headingrr_PerformanceTableHeading
Performance Table Uses Highest Federal Raterr_PerformanceTableUsesHighestFederalRateThe after-tax returns shown in the table are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferredrr_PerformanceTableNotRelevantToTaxDeferredAc­tual after-tax returns depend on the investor's tax situation and  may differ from those shown. The after-tax returns are  not  relevant  to  investors who  hold  their Fund shares through tax-deferred arrangements such  as 401(k) plans or individual retirement accounts, or to investors who  are tax exempt.
Performance Table Narrativerr_PerformanceTableNarrativeTextBlock
Investor Share Class | FAM Value Fund | Russell 2000 Index
 
Risk/Return:rr_RiskReturnAbstract 
1 YEARrr_AverageAnnualReturnYear0126.85%
5 YEARSrr_AverageAnnualReturnYear054.47%
10 YEARSrr_AverageAnnualReturnYear106.33%

Risk_Return Summary - (FAM Equity-Income Fund) (Investor Share Class)
v2.2.0.25
Investor Share Class | FAM Equity-Income Fund
Shareholder Fees -
Investor Share Class
FAM Equity-Income Fund
Investor Class
Maximum sales charge (load) on purchasenone
Maximum deferred sales charge (load)none
Redemption feenone
Annual Fund Operating Expenses -
Investor Share Class
FAM Equity-Income Fund
Investor Class
Management Fees1.00%
Distribution and Service (12b-1) Feesnone
Other expenses[1]0.40%
Acquired Fund Fees and Expenses0.01%
Total Annual Fund Operating Expenses1.41%
Fee Waiver and/or Expense Reimbursement0.01%
Total annual fund operating expenses after fee waiver and/or expense reimbursement1.40%
[1] FAM has entered into a contractual agreement with FAM Equity-Income Fund to limit the total operating expenses of the Fund's Investor Class shares to 1.40% of its average daily net assets through May 1, 2012. This expense limitation agreement may only be amended by the Fund's Board of Trustees. The expense limitation does not limit acquired fund fees and expenses.
Expense Example - (USD $)
1 YEAR
3 YEARS
5 YEARS
10 YEARS
Investor Share Class FAM Equity-Income Fund Investor Class
1444467711,691
Annual Total Return:
Bar Chart
Average Annual Total Returns - Investor Share Class FAM Equity-Income Fund
1 YEAR
5 YEARS
10 YEARS
Investor Class
17.47%0.78%5.94%
Investor Class Return after taxes on distributions
16.62%(0.12%)5.23%
Investor Class Return after taxes on distributions and sale of fund share
11.32%0.33%4.88%
Russell 2000 Index
26.85%4.47%6.33%

Risk_Return Detail Data - (FAM Equity-Income Fund) (Investor Share Class)
v2.2.0.25
LabelElementValue
Risk/Return:rr_RiskReturnAbstract 
Registrant Namedei_EntityRegistrantNameFENIMORE ASSET MANAGEMENT TRUST
Prospectus Daterr_ProspectusDateMay 01, 2011
Investor Share Class | FAM Equity-Income Fund | Investor Class
 
Risk/Return:rr_RiskReturnAbstract 
Maximum sales charge (load) on purchaserr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricenone
Maximum deferred sales charge (load)rr_MaximumDeferredSalesChargeOverOfferingPricenone
Redemption feerr_RedemptionFeeOverRedemptionnone
Management Feesrr_ManagementFeesOverAssets1.00%
Distribution and Service (12b-1) Feesrr_DistributionAndService12b1FeesOverAssetsnone
Other expensesrr_OtherExpensesOverAssets0.40%[1]
Acquired Fund Fees and Expensesrr_AcquiredFundFeesAndExpensesOverAssets0.01%
Total Annual Fund Operating Expensesrr_ExpensesOverAssets1.41%
Fee Waiver and/or Expense Reimbursementrr_FeeWaiverOrReimbursementOverAssets0.01%
Total annual fund operating expenses after fee waiver and/or expense reimbursementrr_NetExpensesOverAssets1.40%
1 YEARrr_ExpenseExampleYear01 144
3 YEARSrr_ExpenseExampleYear03446
5 YEARSrr_ExpenseExampleYear05771
10 YEARSrr_ExpenseExampleYear10 1,691
Annual Return 2001rr_AnnualReturn200120.79%
Annual Return 2002rr_AnnualReturn2002(2.25%)
Annual Return 2003rr_AnnualReturn200320.30%
Annual Return 2004rr_AnnualReturn200414.04%
Annual Return 2005rr_AnnualReturn20055.75%
Annual Return 2006rr_AnnualReturn20066.57%
Annual Return 2007rr_AnnualReturn2007(3.64%)
Annual Return 2008rr_AnnualReturn2008(29.04%)
Annual Return 2009rr_AnnualReturn200921.43%
Annual Return 2010rr_AnnualReturn201017.47%
Highest Quarterly Return, Labelrr_HighestQuarterlyReturnLabelBest Quarter
Highest Quarterly Return, Daterr_BarChartHighestQuarterlyReturnDateJun. 30, 2009
Highest Quarterly Returnrr_BarChartHighestQuarterlyReturn16.68%
Lowest Quarterly Return, Labelrr_LowestQuarterlyReturnLabelWorst Quarter
Lowest Quarterly Return, Daterr_BarChartLowestQuarterlyReturnDateDec. 31, 2008
Lowest Quarterly Returnrr_BarChartLowestQuarterlyReturn(21.88%)
1 YEARrr_AverageAnnualReturnYear0117.47%
5 YEARSrr_AverageAnnualReturnYear050.78%
10 YEARSrr_AverageAnnualReturnYear105.94%
Investor Share Class | FAM Equity-Income Fund | Investor Class | Return after taxes on distributions
 
Risk/Return:rr_RiskReturnAbstract 
1 YEARrr_AverageAnnualReturnYear0116.62%
5 YEARSrr_AverageAnnualReturnYear05(0.12%)
10 YEARSrr_AverageAnnualReturnYear105.23%
Investor Share Class | FAM Equity-Income Fund | Investor Class | Return after taxes on distributions and sale of fund share
 
Risk/Return:rr_RiskReturnAbstract 
1 YEARrr_AverageAnnualReturnYear0111.32%
5 YEARSrr_AverageAnnualReturnYear050.33%
10 YEARSrr_AverageAnnualReturnYear104.88%
Investor Share Class | FAM Equity-Income 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
Portfolio Turnover [Heading]rr_PortfolioTurnoverHeading
Portfolio Turnover [Text Block]rr_PortfolioTurnoverTextBlock
Portfolio Turnover, Raterr_PortfolioTurnoverRate13.38%
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_RiskLoseMoneythe value of your investment will go up and down, which means that you could lose money.
Bar Chart and Performance Table [Heading]rr_BarChartAndPerformanceTableHeadingAnnual Total Return:
Performance Narrative [Text Block]rr_PerformanceNarrativeTextBlock
Performance Information Illustrates Variability of Returns [Text]rr_PerformanceInformationIllustratesVariabilityOfReturnsThe bar chart shows changes in the Investor Share Class performance since 2001. The table shows how Investor Class shares' average annual returns  (before and after taxes) for the of one year, five year and ten year periods compared  to those of the Russell 2000 Index.
Performance Availability Website Address [Text]rr_PerformanceAvailabilityWebSiteAddresswww.famfunds.com
Performance Past Does Not Indicate Future [Text]rr_PerformancePastDoesNotIndicateFutureThe Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]rr_BarChartHeading
Bar Chart Closing [Text Block]rr_BarChartClosingTextBlock
Performance Table Headingrr_PerformanceTableHeading
Performance Table Uses Highest Federal Raterr_PerformanceTableUsesHighestFederalRateThe after-tax returns shown in the table  are calculated using the historical highest  individual federal  marginal income  tax rates, and do not reflect the impact  of state  and  local taxes.
Performance Table Not Relevant to Tax Deferredrr_PerformanceTableNotRelevantToTaxDeferredAc­tual after-tax returns depend on the investor's tax situation and may differ from those shown. The after-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements such  as 401(k) plans or individual retirement accounts, or to inves­tors who are tax exempt.
Performance Table Narrativerr_PerformanceTableNarrativeTextBlock
Investor Share Class | FAM Equity-Income Fund | Russell 2000 Index
 
Risk/Return:rr_RiskReturnAbstract 
1 YEARrr_AverageAnnualReturnYear0126.85%
5 YEARSrr_AverageAnnualReturnYear054.47%
10 YEARSrr_AverageAnnualReturnYear106.33%
[1] FAM has entered into a contractual agreement with FAM Equity-Income Fund to limit the total operating expenses of the Fund's Investor Class shares to 1.40% of its average daily net assets through May 1, 2012. This expense limitation agreement may only be amended by the Fund's Board of Trustees. The expense limitation does not limit acquired fund fees and expenses.