| Shareholder Report | 12 Months Ended |
| Jul. 31, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| 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 | Jul. 31, 2024 |
| Columbia Ultra Short Term Bond Fund Class A | |
| Shareholder Report [Line Items] | |
| Fund Name | Columbia Ultra Short Term Bond Fund |
| Class Name | Class A |
| Trading Symbol | CUSOX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Columbia Ultra Short Term Bond Fund (the Fund) for the period of August 1, 2023 to July 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature 1-800-345-6611. |
| 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) Class Cost of a $10,000 investment Cost paid as a percentage of a $10,000 investment Class A $ 0.45 % |
| Expenses Paid, Amount | $ 46 |
| Expense Ratio, Percent | 0.45% |
| Factors Affecting Performance [Text Block] | Management's Discussion of Fund Performance The performance of Class A shares for the period presented is shown in the Average Annual Top Performance Contributors Allocation and Security selection Mortgage-backed securities Asset-backed securities Investment-grade corporates Top Performance Detractors Duration and Yield-curve positioning |
| Performance Past Does Not Indicate Future [Text] | Past performance does not guarantee future performance. |
| Line Graph [Table Text Block] | Fund Performance The following shows the change in value of a hypothetical $10,000 investment in Class A shares of the Fund during the stated time period. Growth of $10,000 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns (%) 1 year 5 years 10 years Class A (a),(b) 6.30 2.51 1.77 Bloomberg U.S. Short-Term Government/Corporate Index 5.59 2.25 1.70 Bloomberg U.S. Aggregate Bond Index 5.10 0.19 1.61 (a) The returns shown for periods prior to February 20, 2019 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional 3 Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. Please visit columbiathreadneedleus.com/investor/investment-products/mutual-funds/appended-performance (b) Effective August 1, 2024, the Fund compares its performance to the Bloomberg U.S. Aggregate Bond Index |
| No Deduction of Taxes [Text Block] | Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. |
| Updated Performance Information Location [Text Block] | Visit columbiathreadneedleus.com/investment-products/mutual-funds |
| Net Assets | $ 1,046,617,355 |
| Holdings Count | Holding | 234 |
| Advisory Fees Paid, Amount | $ 2,359,256 |
| Investment Company, Portfolio Turnover | 81% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Fund net assets $ Total number of portfolio holdings 234 Management services fees $ Portfolio turnover for the reporting period 81% |
| Holdings [Text Block] | Graphical Representation of Fund 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. Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are available from only two rating agencies, the lower rating is used. When a rating is available from only one rating agency, that rating is used. If a security is not rated by Moody's, S&P and Fitch, but has a rating by Kroll and/or DBRS, the same methodology is applied to those bonds that w ould o Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % Asset Categories Credit Quality |
| Credit Quality Explanation [Text Block] | Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are available from only two rating agencies, the lower rating is used. When a rating is available from only one rating agency, that rating is used. If a security is not rated by Moody's, S&P and Fitch, but has a rating by Kroll and/or DBRS, the same methodology is applied to those bonds that w ould o |
| Largest Holdings [Text Block] | Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % |
| Columbia Ultra Short Term Bond Fund Advisor Class | |
| Shareholder Report [Line Items] | |
| Fund Name | Columbia Ultra Short Term Bond Fund |
| Class Name | Advisor Class |
| Trading Symbol | CUSHX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Columbia Ultra Short Term Bond Fund (the Fund) for the period of August 1, 2023 to July 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature 1-800-345-6611. |
| 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) Class Cost of a $10,000 investment Cost paid as a percentage of a $10,000 investment Advisor Class $ 0.30 % |
| Expenses Paid, Amount | $ 31 |
| Expense Ratio, Percent | 0.30% |
| Factors Affecting Performance [Text Block] | Management's Discussion of Fund Performance The performance of Advisor Class shares for the period presented is shown in the Average Annual Total Returns table. Top Performance Contributors Allocation and Security selection Mortgage-backed securities Asset-backed securities Investment-grade corporates Top Performance Detractors Duration and Yield-curve positioning |
| Performance Past Does Not Indicate Future [Text] | Past performance does not guarantee future performance. |
| Line Graph [Table Text Block] | Fund Performance The following shows the change in value of a hypothetical $10,000 investment in Advisor Class shares of the Fund during the stated time period. Growth of $10,000 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns (%) 1 year 5 years 10 years Advisor Class (a),(b) 6.45 2.66 1.93 Bloomberg U.S. Short-Term Government/Corporate Index 5.59 2.25 1.70 Bloomberg U.S. Aggregate Bond Index 5.10 0.19 1.61 (a) The returns shown for periods prior to December 3, 2018 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional 3 Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. Please visit columbiathreadneedleus.com/investor/investment-products/mutual-funds/appended-performance (b) Effective August 1, 2024, the Fund compares its performance to the Bloomberg U.S. Aggregate Bond Index, a broad-based performance index that meets new regulatory requirements. The Fund’s performance is also compared to its prior benchmark, which more closely represents the market sectors |
| No Deduction of Taxes [Text Block] | Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. |
| Updated Performance Information Location [Text Block] | Visit columbiathreadneedleus.com/investment-products/mutual-funds |
| Net Assets | $ 1,046,617,355 |
| Holdings Count | Holding | 234 |
| Advisory Fees Paid, Amount | $ 2,359,256 |
| Investment Company, Portfolio Turnover | 81% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Fund net assets $ Total number of portfolio holdings 234 Management services fees $ Portfolio turnover for the reporting period 81% |
| Holdings [Text Block] | Graphical Representation of Fund 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 Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are available from only two rating agencies, the lower rating is used. When a rating is available from only one rating agency, that rating is used. If a security is not rated by Moody's, S& to age nc Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % Asset Categories Credit Quality |
| Credit Quality Explanation [Text Block] | Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are available from only two rating agencies, the lower rating is used. When a rating is available from only one rating agency, that rating is used. If a security is not rated by Moody's, S& to age nc |
| Largest Holdings [Text Block] | Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % |
| Columbia Ultra Short Term Bond Fund Institutional Class | |
| Shareholder Report [Line Items] | |
| Fund Name | Columbia Ultra Short Term Bond Fund |
| Class Name | Institutional Class |
| Trading Symbol | CUSBX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Columbia Ultra Short Term Bond Fund (the Fund) for the period of August 1, 2023 to July 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature 1-800-345-6611. |
| 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) Class Cost of a $10,000 investment Cost paid as a percentage of a $10,000 investment Institutional Class $ 0.30 % |
| Expenses Paid, Amount | $ 31 |
| Expense Ratio, Percent | 0.30% |
| Factors Affecting Performance [Text Block] | Management's Discussion of Fund Performance The performance of Institutional Class shares for the period presented is shown in the Average Annual Total Returns table. Top Performance Contributors Allocation and Security selection Mortgage-backed securities Asset-backed securities Investment-grade corporates Top Performance Detractors Duration and Yield-curve positioning |
| Performance Past Does Not Indicate Future [Text] | Past performance does not guarantee future performance. |
| Line Graph [Table Text Block] | Growth of $10,000 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns (%) 1 year 5 years 10 years Institutional Class (a),(b) 6.45 2.66 1.94 Bloomberg U.S. Short-Term Government/Corporate Index 5.59 2.25 1.70 Bloomberg U.S. Aggregate Bond Index 5.10 0.19 1.61 (a) The returns shown for periods prior to December 3, 2018 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional 3 Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. Please visit columbiathreadneedleus.com/investor/investment-products/mutual-funds/appended-performance (b) Effective August 1, 2024, the Fund compares its performance to the Bloomberg U.S. Aggregate Bond Index, a broad-based performance index that meets new regulatory requirements. The Fund’s performance is also compared to its prior benchmark, which more closely represents the market sectors and/or asset classes in which the Fund primarily invests. |
| No Deduction of Taxes [Text Block] | Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. |
| Updated Performance Information Location [Text Block] | Visit columbiathreadneedleus.com/investment-products/mutual-funds |
| Net Assets | $ 1,046,617,355 |
| Holdings Count | Holding | 234 |
| Advisory Fees Paid, Amount | $ 2,359,256 |
| Investment Company, Portfolio Turnover | 81% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Fund net assets $ Total number of portfolio holdings 234 Management services fees $ Portfolio turnover for the reporting period 81% |
| Holdings [Text Block] | Graphical Representation of Fund 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. Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are available from only two rating agencies, the lower rating is used. When a rating is available from only one rating agency, that rating is used. If a security is not rated by Moody's, S&P and Fitch, but has a rating by Kroll and/or DBRS, the same methodology is applied to those bonds that would otherwise be not rated. When a bond is not rated by any rating agency, it is designated as “Not rated.” Credit quality ratings assigned ting Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % Asset Categories Credit Quality |
| Credit Quality Explanation [Text Block] | Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are available from only two rating agencies, the lower rating is used. When a rating is available from only one rating agency, that rating is used. If a security is not rated by Moody's, S&P and Fitch, but has a rating by Kroll and/or DBRS, the same methodology is applied to those bonds that would otherwise be not rated. When a bond is not rated by any rating agency, it is designated as “Not rated.” Credit quality ratings assigned ting |
| Largest Holdings [Text Block] | Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % |
| Columbia Ultra Short Term Bond Fund Institutional 3 Class | |
| Shareholder Report [Line Items] | |
| Fund Name | Columbia Ultra Short Term Bond Fund |
| Class Name | Institutional 3 Class |
| Trading Symbol | CMGUX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Columbia Ultra Short Term Bond Fund (the Fund) for the period of August 1, 2023 to July 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature 1-800-345-6611. |
| 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) Class Cost of a $10,000 investment Cost paid as a percentage of a $10,000 investment Institutional 3 Class $ 0.24 % |
| Expenses Paid, Amount | $ 25 |
| Expense Ratio, Percent | 0.24% |
| Factors Affecting Performance [Text Block] | Management's Discussion of Fund Performance The performance of Institutional 3 Class shares for the period presented is shown in the Average Annual Total Returns table. Top Performance Contributors Allocation and Security selection Mortgage-backed securities Asset-backed securities Investment-grade corporates Top Performance Detractors Duration and Yield-curve positioning |
| Performance Past Does Not Indicate Future [Text] | Past performance does not guarantee future performance. |
| Line Graph [Table Text Block] | Growth of $10,000 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns (%) 1 year 5 years 10 years Institutional 3 Class (a) 6.40 2.71 2.01 Bloomberg U.S. Short-Term Government/Corporate Index 5.59 2.25 1.70 Bloomberg U.S. Aggregate Bond Index 5.10 0.19 1.61 (a) Effective August 1, 2024, the Fund compares its performance to the Bloomberg U.S. Aggregate Bond Index, a broad |
| No Deduction of Taxes [Text Block] | Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. |
| Updated Performance Information Location [Text Block] | Visit columbiathreadneedleus.com/investment-products/mutual-funds |
| Net Assets | $ 1,046,617,355 |
| Holdings Count | Holding | 234 |
| Advisory Fees Paid, Amount | $ 2,359,256 |
| Investment Company, Portfolio Turnover | 81% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Fund net assets $ Total number of portfolio holdings 234 Management services fees $ Portfolio turnover for the reporting period 81% |
| Holdings [Text Block] | Graphical Representation of Fund 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. Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are avai lable rating subjective statements Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % Asset Categories Credit Quality |
| Credit Quality Explanation [Text Block] | Bond ratings on Fund holdings are divided into categories ranging from highest to lowest credit quality, determined by using the middle rating of Moody’s, S&P and Fitch, after dropping the highest and lowest available ratings. When ratings are avai lable rating subjective statements |
| Largest Holdings [Text Block] | Top Holdings VCAT LLC 1.5 % Santander Drive Auto Receivables Trust 1.5 % Carmax Auto Owner Trust 1.4 % Verizon Master Trust 1.4 % Carvana Auto Receivables Trust 1.3 % Carvana Auto Receivables Trust 1.2 % Towd Point Mortgage Trust 1.1 % Verizon Master Trust 1.1 % VCAT Asset Securitization LLC 1.1 % Enterprise Fleet Financing LLC 1.1 % |
