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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName DFA INVESTMENT DIMENSIONS GROUP INC
Prospectus Date rr_ProspectusDate Jul. 12, 2011
U.S. Targeted Value Portfolio | Class R10
 
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees (fees paid directly from your investment) rr_MaximumAccountFee none
Management Fee rr_ManagementFeesOverAssets 0.35%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.10%
Other Expenses rr_OtherExpensesOverAssets 0.40% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.85%
Fee Waiver and/or Expense Reimbursement or (Recovery) rr_FeeWaiverOrReimbursementOverAssets 0.25% [2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement or (Recovery) rr_NetExpensesOverAssets 0.60%
1 Year rr_ExpenseExampleYear01 61
3 Years rr_ExpenseExampleYear03 246
5 Years rr_ExpenseExampleYear05 447
10 Years rr_ExpenseExampleYear10 1,026
U.S. Targeted Value Portfolio | Class R25
 
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees (fees paid directly from your investment) rr_MaximumAccountFee none
Management Fee rr_ManagementFeesOverAssets 0.35%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.59% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.19%
Fee Waiver and/or Expense Reimbursement or (Recovery) rr_FeeWaiverOrReimbursementOverAssets 0.44% [2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement or (Recovery) rr_NetExpensesOverAssets 0.75%
1 Year rr_ExpenseExampleYear01 77
3 Years rr_ExpenseExampleYear03 334
5 Years rr_ExpenseExampleYear05 612
10 Years rr_ExpenseExampleYear10 1,404
U.S. Targeted Value Portfolio | Institutional Class
 
Risk/Return: rr_RiskReturnAbstract  
Annual Return 2001 rr_AnnualReturn2001 17.93% [3]
Annual Return 2002 rr_AnnualReturn2002 (9.66%) [3]
Annual Return 2003 rr_AnnualReturn2003 54.07% [3]
Annual Return 2004 rr_AnnualReturn2004 24.68% [3]
Annual Return 2005 rr_AnnualReturn2005 9.25% [3]
Annual Return 2006 rr_AnnualReturn2006 19.70% [3]
Annual Return 2007 rr_AnnualReturn2007 (8.19%) [3]
Annual Return 2008 rr_AnnualReturn2008 (33.78%) [3]
Annual Return 2009 rr_AnnualReturn2009 31.88% [3]
Annual Return 2010 rr_AnnualReturn2010 29.01% [3]
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2003
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.65%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.48%)
One Year rr_AverageAnnualReturnYear01 29.01%
Five Years rr_AverageAnnualReturnYear05 4.36%
Ten Years rr_AverageAnnualReturnYear10 10.72%
U.S. Targeted Value Portfolio
 
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 February 28, 2012
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 20.00%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates The Class R10 shares and Class R25 shares are each a new class of shares of the Portfolio, so the "Other Expenses" shown for each class are based on anticipated fees and expenses for the fiscal period ending October 31, 2011
Expense Example [Heading] rr_ExpenseExampleHeading
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
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 Because the value of your investment in the Portfolio will fluctuate, there is the risk that you will lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart shows the changes in performance of the Institutional Class shares of the Portfolio from year to year. The table illustrates how annualized one year, five year and ten year returns of the Institutional Class shares of the Portfolio compare with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.dimensional.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The U.S. Targeted Value Portfolio's past performance (before and after taxes) is not an indication of future results.
Bar Chart [Heading] rr_BarChartHeading
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Performance Table Heading rr_PerformanceTableHeading
U.S. Targeted Value Portfolio | Russell 2000 Value Index (reflects no deduction for fees, expenses, or taxes)
 
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 24.50%
Five Years rr_AverageAnnualReturnYear05 3.52%
Ten Years rr_AverageAnnualReturnYear10 8.42%
[1] The Class R10 shares and Class R25 shares are each a new class of shares of the Portfolio, so the "Other Expenses" shown for each class are based on anticipated fees and expenses for the fiscal period ending October 31, 2011.
[2] The Advisor has contractually agreed to reduce all or a portion of its administration fee and investment advisory fee and to assume the direct and indirect expenses of a class of the U.S. Targeted Value Portfolio (excluding the expenses the Portfolio incurs indirectly through investment in other investment companies and excluding applicable 12b-1 fees) to the extent necessary to limit the annualized expenses of the Portfolio to 0.50% (the "Annualized Expense Ratio"). At any time that the annualized expenses (excluding applicable 12b-1 fees) of the Portfolio are less than the Annualized Expense Ratio, the Advisor retains the right to seek reimbursement for any fees previously waived and/or expenses previously assumed to the extent that the amount of such reimbursement does not cause the Annualized Expense Ratio of the Portfolio to exceed the Annualized Expense Ratio. The Portfolio is not obligated to reimburse the Advisor for fees previously waived or expenses previously assumed by the Advisor more than thirty-six months before the date of such reimbursement. The Fee Waiver and Expense Assumption Agreement for the U.S. Targeted Value Portfolio will remain in effect through February 28, 2012, and may not be terminated by the Advisor prior to that date.
[3] The Institutional Class shares of the Portfolio would have substantially similar annual returns as the ClassR10 shares and Class R25 shares because the shares are invested in the same portfolio securities. Returns for the Class R10 shares, Class R25 shares, and Institutional Class shares will differ to the extent that the classes will have different expenses, and returns for the Class R10 shares and Class R25 shares would be expected to be lower than the returns of the Institutional Class shares to the extent that the Class R10 shares and Class R25 shares have higher expenses than the Institutional Class shares.