Label

Element

Value

Risk/Return:

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Registrant Name

dei_EntityRegistrantName

COLUMBIA FUNDS SERIES TRUST I

Prospectus Date

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Jan. 01, 2021

Supplement to Prospectus [Text Block]

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Supplement dated December 16, 2021

to the Prospectus, Summary Prospectus and Statement of Additional Information (SAI), each as supplemented, if applicable, of the following Fund:

Fund	Document Dated
Columbia Funds Series Trust I
Multi-Manager Small Cap Equity Strategies Fund	Prospectus: 1/1/2021 Summary Prospectus: 1/1/2021 SAI: 12/1/2021

In connection with the decision by BMO Asset Management Corp. (the Subadviser) to exit the mutual fund investment advisory business in the United States, the Subadviser’s portfolio managers who currently manage the portion of the Fund allocated to the Subadviser (the BMO – Disciplined Small Cap Value Strategy Sleeve, or the Applicable Sleeve) are expected to remain as portfolio managers of the Applicable Sleeve while becoming employees of the Fund’s investment manager, Columbia Management Investment Advisers, LLC (Columbia Management), on or about December 16, 2021 (the Transfer Date).  Upon the Transfer Date, Columbia Management will assume day-to-day portfolio management responsibility with respect to the Applicable Sleeve, which will be renamed Columbia Management – Integrated Small Cap Value Strategy Sleeve. Additionally, all references to BMO Asset Management Corp. as a subadviser of the Fund are hereby deleted from the Fund's prospectus, summary prospectus, and SAI.

Multi-Manager Small Cap Equity Strategies Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement to Prospectus [Text Block]

rr_SupplementToProspectusTextBlock

Supplement dated December 16, 2021

to the Prospectus, Summary Prospectus and Statement of Additional Information (SAI), each as supplemented, if applicable, of the following Fund:

Fund	Document Dated
Columbia Funds Series Trust I
Multi-Manager Small Cap Equity Strategies Fund	Prospectus: 1/1/2021 Summary Prospectus: 1/1/2021 SAI: 12/1/2021

In connection with the decision by BMO Asset Management Corp. (the Subadviser) to exit the mutual fund investment advisory business in the United States, the Subadviser’s portfolio managers who currently manage the portion of the Fund allocated to the Subadviser (the BMO – Disciplined Small Cap Value Strategy Sleeve, or the Applicable Sleeve) are expected to remain as portfolio managers of the Applicable Sleeve while becoming employees of the Fund’s investment manager, Columbia Management Investment Advisers, LLC (Columbia Management), on or about December 16, 2021 (the Transfer Date).  Upon the Transfer Date, Columbia Management will assume day-to-day portfolio management responsibility with respect to the Applicable Sleeve, which will be renamed Columbia Management – Integrated Small Cap Value Strategy Sleeve. Additionally, all references to BMO Asset Management Corp. as a subadviser of the Fund are hereby deleted from the Fund's prospectus, summary prospectus, and SAI.