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Institutional Class Prospectus | Boston Partners Global Equity Fund  
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] ck0000831114_SupplementTextBlock

THE RBB FUND, INC.


Boston Partners Investment Funds


Boston Partners Global Equity Fund


Institutional Class


(INVESTMENT PORTFOLIO OF THE RBB FUND, INC.)


Supplement dated June 29, 2016


to the Prospectuses dated February 29, 2016


THIS SUPPLEMENT CONTAINS NEW AND ADDITIONAL INFORMATION BEYOND THAT CONTAINED IN THE PROSPECTUS AND SHOULD BE READ IN CONJUNCTION WITH THE PROSPECTUS.
Risk/Return [Heading] rr_RiskReturnHeading Boston Partners Global Equity Fund
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Effective immediately, the section “SUMMARY SECTION — BOSTON PARTNERS GLOBAL EQUITY FUND — Performance Information — Average Annual Total Returns” on page 35 of the Investor Class Prospectus and page 41 of the Institutional Class Prospectus is deleted and replaced with the following:
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The table, like the bar chart, provides some indication of the risks of investing in the Fund by showing how the Fund’s average annual total returns for the one year and since inception periods compare with those of a broad measure of market performance.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns 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 Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund’s Institutional Class both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

Please retain this Supplement for future reference.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (for the Periods Ended December 31, 2015)
Institutional Class Prospectus | Boston Partners Global Equity Fund | MSCI World Index (reflects no deduction for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns,1 Year rr_AverageAnnualReturnYear01 (0.32%)
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 11.88%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2011
Institutional Class Prospectus | Boston Partners Global Equity Fund | Institutional Class  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns,1 Year rr_AverageAnnualReturnYear01 0.80%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 12.62%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2011
Institutional Class Prospectus | Boston Partners Global Equity Fund | Institutional Class | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns,1 Year rr_AverageAnnualReturnYear01 0.69% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 11.93% [1]
Institutional Class Prospectus | Boston Partners Global Equity Fund | Institutional Class | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns,1 Year rr_AverageAnnualReturnYear01 0.54%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.87%
[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The table, like the bar chart, provides some indication of the risks of investing in the Fund by showing how the Fund's average annual total returns for the one year and since inception periods compare with those of a broad measure of market performance.