v3.26.3
Performance Management - BRUCE FUND
Oct. 26, 2026
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance
Performance Narrative [Text Block]

The bar chart below shows how the Fund’s investment results have varied from year to year. The table below shows how the Fund’s average annual total returns compare over time to those of a broad-based securities market index. This information provides some indication of the risks of investing in the Fund. Past performance of the Fund before and after tax is not necessarily an indication of how it will perform in the future. Current performance of the Fund may be lower or higher than the performance quoted below. Updated performance information may be obtained by calling (800) 872-7823.
Performance Past Does Not Indicate Future [Text] Past performance of the Fund before and after tax is not necessarily an indication of how it will perform in the future.
Performance Information Illustrates Variability of Returns [Text] The bar chart below shows how the Fund’s investment results have varied from year to year. The table below shows how the Fund’s average annual total returns compare over time to those of a broad-based securities market index.
Bar Chart [Table]

(BAR CHAT)

 
Bar Chart Closing [Text Block]

During the period shown in the bar chart, the highest return for a quarter was 11.09% during the quarter ended December 31, 2020 and the lowest return for a quarter was (10.79)% during the quarter ended March 31, 2020. The Fund’s year to date return as of September 30th was 15.64%.

 
Year to Date Return, Label [Optional Text] The Fund’s year to date return
Bar Chart, Year to Date Return 15.64%
Bar Chart, Year to Date Return, Date Sep. 30, 2026
Highest Quarterly Return, Label [Optional Text] the highest return for a quarter
Highest Quarterly Return 11.09%
Highest Quarterly Return, Date Dec. 31, 2020
Lowest Quarterly Return, Label [Optional Text] the lowest return for a quarter
Lowest Quarterly Return (10.79%)
Lowest Quarterly Return, Date Mar. 31, 2020
Performance Table Heading Average Annual Total Returns for the periods ending December 31, 2025
Performance Table Uses Highest Federal Rate After-tax returns are calculated using the historical highest individual federal income tax rates in effect and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).
Performance [Table]
Bruce Fund 1 Year 5 Years 10 Years
Return Before Taxes 14.88% 5.01% 7.01%
Return After Taxes on Distributions 13.12% 3.05% 5.42%
Return After Taxes on Distributions and Sale of Fund Shares 9.87% 3.63% 5.31%
       
S&P 500 Stock Index
(reflects no deduction for fees)		 17.88% 14.42% 14.82%
Index No Deduction for Fees, Expenses, or Taxes [Text] reflects no deduction for fees
Performance Table Closing [Text Block]

After-tax returns are calculated using the historical highest individual federal income tax rates in effect and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).

 

Current performance of the Fund may be lower or higher than the performance quoted above. Updated performance information may be obtained by calling (800) 872-7823.
Performance Availability Phone [Text] (800) 872-7823