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Shareholder Report
 6 Months Ended
Oct. 31, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Columbia Funds Series Trust I
Entity Central Index Key 0000773757
Entity Investment Company Type N-1A
Document Period End Date Oct. 31, 2025
Columbia Bond Fund - Class A  
Shareholder Report [Line Items]  
Fund Name Columbia Bond Fund
Class Name Class A
Trading Symbol CNDAX
Annual or Semi-Annual Statement [Text Block] This
semi-annual shareholder report
contains important information about Columbia Bond Fund (the Fund) for the period of May 1, 2025 to October 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at
columbiathreadneedleus.com/resources/literature
. You can also request more information by contacting us at
1-800-345-6611
.
Material Fund Change Notice [Text Block] This report describes certain changes to the Fund that are planned or have occurred since the beginning of the reporting period.
Additional Information Phone Number 1-800-345-6611
Additional Information Website columbiathreadneedleus.com/resources/literature
Expenses [Text Block]
What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)
ClassCost of a $10,000 investmentCost paid as a percentage of a $10,000 investment
Class A
$
41
0.80
%
(a)
(a)
Annualized.
Expenses Paid, Amount $ 41
Expense Ratio, Percent 0.80% [1]
Net Assets $ 1,370,781,092
Holdings Count | Holding 455
Investment Company, Portfolio Turnover 114.00%
Additional Fund Statistics [Text Block]
Key Fund
Statistics
Fund net assets
$
1,370,781,092
Total number of portfolio holdings
455
Portfolio turnover for the reporting period
114%
Portfolio turnover for the reporting period excluding to be announced (TBA) securities
20%
Holdings [Text Block]
Graphical Representation of Fund
 
Holdings
The tables below show the investment makeup of the Fund
represented
as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Asset Categories
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Material Fund Change [Text Block]
Certain Fund Changes
This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
At a meeting held on September 5, 2025, the Board of Trustees of Columbia Funds Series Trust I approved an Agreement and Plan of Reorganization pursuant to which the Fund will transfer all of its assets and liabilities to Columbia Core Bond ETF (the Acquiring Fund) in exchange for shares of the Acquiring Fund (the Reorganization). The Reorganization does not require shareholder approval and is expected to close on or about March 16, 2026.
As a result of the Reorganization, Class A incurred 0.06% in reorganizational expenses, which had an impact of a 0.06% increase to the net expense ratio during the current reporting period.
Summary of Change Legend [Text Block] This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
Updated Prospectus Phone Number 1-800-345-6611
Updated Prospectus Web Address columbiathreadneedleus.com/resources/literature
Columbia Bond Fund - Institutional Class  
Shareholder Report [Line Items]  
Fund Name Columbia Bond Fund
Class Name Institutional Class
Trading Symbol UMMGX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Columbia Bond Fund (the Fund) for the period of May 1, 2025 to October 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at
columbiathreadneedleus.com/resources/literature
. You can also request more information by contacting us at
1-800-345-6611.
Material Fund Change Notice [Text Block] This report describes certain changes to the Fund that are planned or have occurred since the beginning of the reporting period.
Additional Information Phone Number 1-800-345-6611
Additional Information Website columbiathreadneedleus.com/resources/literature
Expenses [Text Block]
What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)
ClassCost of a $10,000 investmentCost paid as a percentage of a $10,000 investment
Institutional Class
$
26		0.51
%
(a)
(a)
Annualized.
Expenses Paid, Amount $ 26
Expense Ratio, Percent 0.51% [1]
Net Assets $ 1,370,781,092
Holdings Count | Holding 455
Investment Company, Portfolio Turnover 114.00%
Additional Fund Statistics [Text Block]
Key Fund
Statistics
Fund net assets
$
1,370,781,092
Total number of portfolio holdings
455
Portfolio turnover for the reporting period
114%
Portfolio turnover for the reporting period excluding to be announced (TBA) securities
20%
Holdings [Text Block]
Graphical Representation of Fund
 
Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Asset Categories
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Material Fund Change [Text Block]
Certain Fund Changes
This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
At a meeting held on
September
5, 2025, the Board of Trustees of Columbia Funds Series Trust I approved an Agreement and Plan of Reorganization pursuant to which the Fund will transfer all of its assets and liabilities to Columbia Core Bond ETF (the Acquiring Fund) in exchange for shares of the Acquiring Fund (the Reorganization). The Reorganization does not require shareholder approval and is expected to close on or about
Ma
rch 16, 2026.
Summary of Change Legend [Text Block] This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
Updated Prospectus Phone Number 1-800-345-6611
Updated Prospectus Web Address columbiathreadneedleus.com/resources/literature
Columbia Bond Fund - Institutional 2 Class  
Shareholder Report [Line Items]  
Fund Name Columbia Bond Fund
Class Name Institutional 2 Class
Trading Symbol CNFRX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Columbia Bond Fund (the Fund) for the period of May 1, 2025 to October 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at
columbiathreadneedleus.com/resources/literature
. You can also request more information by contacting us at
1-800-345-6611.
Material Fund Change Notice [Text Block] This report describes certain changes to the Fund that are planned or have occurred since the beginning of the reporting period.
Additional Information Phone Number 1-800-345-6611
Additional Information Website columbiathreadneedleus.com/resources/literature
Expenses [Text Block]
What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)
ClassCost of a $10,000 investmentCost paid as a percentage of a $10,000 investment
Institutional 2 Class
$
24		0.46
%
(a)
(a)
Annualized
.
Expenses Paid, Amount $ 24
Expense Ratio, Percent 0.46% [1]
Net Assets $ 1,370,781,092
Holdings Count | Holding 455
Investment Company, Portfolio Turnover 114.00%
Additional Fund Statistics [Text Block]
Key Fund Statistics
Fund net assets
$
1,370,781,092
Total number of portfolio holdings
455
Portfolio turnover for the reporting period
114%
Portfolio turnover for the reporting period excluding to be announced (TBA) securities
20%
Holdings [Text Block]
Graphical Representation of Fund
 
Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Asset Categories
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Material Fund Change [Text Block]
Certain Fund Changes
This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
At a meeting held on September 5, 2025, the Board of Trustees of Columbia Funds Series Trust I approved an Agreement and Plan of Reorganization pursuant to which the Fund will transfer all of its assets and liabilities to Columbia Core Bond ETF (the Acquiring Fund) in exchange for shares of the Acquiring Fund (the Reorganization). The Reorganization does not require shareholder approval and is expected to close on or about March 16, 2026.
Summary of Change Legend [Text Block] This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
Updated Prospectus Phone Number 1-800-345-6611
Updated Prospectus Web Address columbiathreadneedleus.com/resources/literature
Columbia Bond Fund - Institutional 3 Class  
Shareholder Report [Line Items]  
Fund Name Columbia Bond Fund
Class Name Institutional 3 Class
Trading Symbol CBFYX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Columbia Bond Fund (the Fund) for the period of May 1, 2025 to October 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at
columbiathreadneedleus.com/resources/literature
. You can also request more information by contacting us at
1-800-345-6611.
Material Fund Change Notice [Text Block] This report describes certain changes to the Fund that are planned or have occurred since the beginning of the reporting period.
Additional Information Phone Number 1-800-345-6611
Additional Information Website columbiathreadneedleus.com/resources/literature
Expenses [Text Block]
What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)
ClassCost of a $10,000 investmentCost paid as a percentage of a $10,000 investment
Institutional 3 Class
$
21		0.40
%
(a)
(a)
Annualized.
Expenses Paid, Amount $ 21
Expense Ratio, Percent 0.40% [1]
Net Assets $ 1,370,781,092
Holdings Count | Holding 455
Investment Company, Portfolio Turnover 114.00%
Additional Fund Statistics [Text Block]
Key Fund Statistics
Fund
net
assets
$
1,370,781,092
Total number of portfolio holdings
455
Portfolio turnover for the reporting period
114%
Portfolio turnover for the reporting period excluding to be announced (TBA) securities
20%
Holdings [Text Block]
Graphical Representation of Fund
 
Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio
composition
is subject to change.
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Asset Categories
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Material Fund Change [Text Block]
Certain Fund Changes
This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
At a meeting held on September 5, 2025, the Board of Trustees of Columbia Funds Series Trust I approved an Agreement and Plan of Reorganization pursuant to which the Fund will transfer all of its assets and liabilities to Columbia Core Bond ETF (the Acquiring Fund) in exchange for shares of the Acquiring Fund (the Reorganization). The Reorganization does not require shareholder approval and is expected to close on or about March 16, 2026.
Summary of Change Legend [Text Block] This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
Updated Prospectus Phone Number 1-800-345-6611
Updated Prospectus Web Address columbiathreadneedleus.com/resources/literature
Columbia Bond Fund - Class S  
Shareholder Report [Line Items]  
Fund Name Columbia Bond Fund
Class Name Class S
Trading Symbol UMMDX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Columbia Bond Fund (the Fund) for the period of May 1, 2025 to October 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at
columbiathreadneedleus.com/resources/literature
. You can also request more information by contacting us at
1-800-345-6611.
Material Fund Change Notice [Text Block] This report describes certain changes to the Fund that are planned or have occurred since the beginning of the reporting period.
Additional Information Phone Number 1-800-345-6611
Additional Information Website columbiathreadneedleus.com/resources/literature
Expenses [Text Block]
What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)
ClassCost of a $10,000 investmentCost paid as a percentage of a $10,000 investment
Class S
$
26		0.51
%
(a)
(a)
Annualized.
Expenses Paid, Amount $ 26
Expense Ratio, Percent 0.51% [1]
Net Assets $ 1,370,781,092
Holdings Count | Holding 455
Investment Company, Portfolio Turnover 114.00%
Additional Fund Statistics [Text Block]
Key Fund
Statistics
Fund net assets
$
1,370,781,092
Total number of portfolio holdings
455
Portfolio turnover for the reporting period
114%
Portfolio turnover for the reporting period excluding to be announced (TBA) securities
20%
Holdings [Text Block]
Graphical Representation of Fund
 
Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Asset Categories
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Holdings
Uniform Mortgage-Backed Security TBA
11/13/2055 6.000%		2.6
%
Federal National Mortgage Association
06/01/2052 3.000%		2.1
%
Uniform Mortgage-Backed Security TBA
11/13/2053 5.500%		1.9
%
Federal National Mortgage Association
12/01/2054 5.000%		1.8
%
Uniform Mortgage-Backed Security TBA
11/14/2054 4.500%		1.6
%
Fannie Mae REMICS
09/25/2055 5.033%		1.4
%
Federal National Mortgage Association
07/01/2055 5.500%		1.3
%
Federal National Mortgage Association
12/01/2054 5.000%		1.2
%
Federal National Mortgage Association
08/01/2052 4.000%		1.1
%
Huntington Bank Auto Credit-Linked Notes
09/20/2033 4.835%		1.0
%
Material Fund Change [Text Block]
Certain Fund Changes
This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
At a meeting held on September 5, 2025, the Board of Trustees of Columbia Funds Series Trust I approved an Agreement and Plan of Reorganization pursuant to which the Fund will transfer all of its assets and liabilities to Columbia Core Bond ETF (the Acquiring Fund) in exchange for shares of the Acquiring Fund (the Reorganization). The Reorganization does not require shareholder approval and is expected to close on or about March 16, 2026.
Summary of Change Legend [Text Block] This is a summary of certain changes to the Fund. For more complete information, you may review the Fund’s prospectus, which is available at
columbiathreadneedleus.com/resources/literature
or upon request at
1-800-345-6611
.
Updated Prospectus Phone Number 1-800-345-6611
Updated Prospectus Web Address columbiathreadneedleus.com/resources/literature
[1] Annualized.