| Shareholder Report | 12 Months Ended |
| Aug. 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 | Aug. 31, 2024 |
| Multi-Manager International Equity Strategies Fund Institutional Class [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Multi-Manager International Equity Strategies Fund |
| Class Name | Institutional Class |
| Trading Symbol | CMIEX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Multi-Manager International Equity Strategies Fund (the Fund) for the period of September 1, 2023 to August 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. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during 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) Class Cost of a $10,000 investment Cost paid as a percentage of a $10,000 investment Institutional Class $ 0.97 % |
| Expenses Paid, Amount | $ 106 |
| Expense Ratio, Percent | 0.97% |
| 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 Stock selection Allocations Individual holdings Top Performance Detractors Stock selection Allocations Individual holdings |
| Performance Past Does Not Indicate Future [Text] | Past performance does not guarantee future performance. |
| Line Graph [Table Text Block] | |
| Average Annual Return [Table Text Block] | Average Annual Total Returns (%) 1 year 5 years Since Fund Institutional Class (a) 18.68 10.11 6.41 MSCI EAFE Index (Net) 19.40 8.61 5.60 (a) The Fund’s performance prior to August 13, 2024 reflects returns achieved by the Investment Manager and all subadvisers other than Walter Scott & Partners Limited (Walter Scott). Thereafter, the Investment Manager and all subadvisers, including Walter Scott, have each managed a portion of the Fund’s portfolio. If the Fund’s current Investment Manager and subadvisers had been in place for the prior periods, results shown may have been different. |
| Performance Inception Date | May 17, 2018 |
| 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. |
| Material Change Date | Aug. 13, 2024 |
| Updated Performance Information Location [Text Block] | Visit columbiathreadneedleus.com/investment-products/mutual-funds |
| Net Assets | $ 2,816,280,118 |
| Holdings Count | Holding | 568 |
| Advisory Fees Paid, Amount | $ 18,786,071 |
| Investment Company, Portfolio Turnover | 67% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Fund net assets $ Total number of portfolio holdings 568 Management services fees $ Portfolio turnover for the reporting period 67% |
| Holdings [Text Block] | Graphical Representation of Fund The tables below show the investment makeup Top Holdings SAP SE 2.0 % Roche Holding AG, Genusschein Shares 2.0 % Rolls-Royce Holdings PLC 1.6 % Samsung Electronics Co., Ltd. 1.4 % Barclays Bank PLC 1.4 % Alstom SA 1.3 % Novo Nordisk A/S, Class B 1.3 % FANUC Corp. 1.2 % BP PLC 1.2 % ASML Holding NV 1.1 % Equity Sector Allocation Geographic Allocation |
| Largest Holdings [Text Block] | Top Holdings SAP SE 2.0 % Roche Holding AG, Genusschein Shares 2.0 % Rolls-Royce Holdings PLC 1.6 % Samsung Electronics Co., Ltd. 1.4 % Barclays Bank PLC 1.4 % Alstom SA 1.3 % Novo Nordisk A/S, Class B 1.3 % FANUC Corp. 1.2 % BP PLC 1.2 % ASML Holding NV 1.1 % |
| Material Fund Change [Text Block] | Certain Fund Changes This is a summary of certain changes to the Fund during the reporting period. For more complete information, you may review the Fund’s prospectus, which is available at columbiathreadneedleus.com/resources/literature Effective August 13, 2024 |
| Material Fund Change Adviser [Text Block] | Effective August 13, 2024 |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund during the reporting period. For more complete information, you may review the Fund’s prospectus, which is available at columbiathreadneedleus.com/resources/literature |
| Updated Prospectus Phone Number | 1-800-345-6611 |
| Updated Prospectus Web Address | columbiathreadneedleus.com/resources/literature |
