Label

Element

Value

Prospectus [Line Items]

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Document Type

dei_DocumentType

497

Document Period End Date

dei_DocumentPeriodEndDate

Dec. 31, 2018

Entity Registrant Name

dei_EntityRegistrantName

RMB INVESTORS TRUST

Entity Central Index Key

dei_EntityCentralIndexKey

0000030126

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Mar. 19, 2020

Document Effective Date

dei_DocumentEffectiveDate

Mar. 19, 2020

Prospectus Date

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May 01, 2019

Entity Inv Company Type

dei_EntityInvCompanyType

N-1A

RMB Mendon Financial Long/Short Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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RMB Mendon Financial Long/Short Fund

Supplement to Prospectus [Text Block]

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RMB FUNDS

RMB Mendon Financial Long/Short Fund

Supplement dated March 19, 2020 to the Prospectus, Summary Prospectus and Statement of Additional Information of RMB Mendon Financial Long/Short Fund (the “Fund”), each dated May 1, 2019.

IMPORTANT NOTICE REGARDING INVESTMENT POLICIES

Effective March 19, 2020, the “Principal Investment Strategies” in the Fund’s Summary Prospectus and the Fund’s summary section of the Prospectus shall include the following language:

As a result of recent market disruptions arising from the rapid and escalating spread of COVID-19, the Fund has experienced significant losses and a decrease in assets. The relatively long positioning of the portfolio coupled with a lack of success in hedging its concentration in smaller cap financials during this severe market drawdown resulted in market losses. As a result, Mendon Capital Advisors Corp. (“Mendon”) has repositioned the portfolio, which includes maintaining a high level of cash and liquidating derivatives and short positions. As a result, the Fund is in a temporary defensive posture as permitted under the Fund’s prospectus. Mendon believes this step will allow the Fund to protect value for shareholders.

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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As a result of recent market disruptions arising from the rapid and escalating spread of COVID-19, the Fund has experienced significant losses and a decrease in assets. The relatively long positioning of the portfolio coupled with a lack of success in hedging its concentration in smaller cap financials during this severe market drawdown resulted in market losses. As a result, Mendon Capital Advisors Corp. (“Mendon”) has repositioned the portfolio, which includes maintaining a high level of cash and liquidating derivatives and short positions. As a result, the Fund is in a temporary defensive posture as permitted under the Fund’s prospectus. Mendon believes this step will allow the Fund to protect value for shareholders.

Supplement Closing [Text Block]

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Please retain this supplement for future reference.

RMB Mendon Financial Long/Short Fund | Class A

Prospectus [Line Items]

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Trading Symbol

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RMBFX

RMB Mendon Financial Long/Short Fund | Class C

Prospectus [Line Items]

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Trading Symbol

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RMBCX

RMB Mendon Financial Long/Short Fund | Class I

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

RMBIX