v3.26.1
Shareholder Report
 12 Months Ended
Jun. 30, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSR
Amendment Flag false
Registrant Name BRUCE FUND INC
Entity Central Index Key 0000047071
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026
Shareholder Report Annual or Semi-Annual Annual Shareholder Report
C000031584  
Shareholder Report [Line Items]  
Fund Name Bruce Fund
Trading Symbol BRUFX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about Bruce Fund for the period of July 1, 2025 to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.thebrucefund.com/document-library. You can also request this information by contacting us at (800) 872-7823.
Additional Information Phone Number (800) 872-7823
Additional Information Website https://www.thebrucefund.com/document-library
Expenses [Text Block]

What were the Fund’s costs for the last year?

(based on a hypothetical $10,000 investment)

Table Summary
Fund Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Bruce Fund
$64
0.56%
Expenses Paid, Amount $ 64
Expense Ratio, Percent 0.56%
Performance Past Does Not Indicate Future [Text] The Fund’s past performance is not a good predictor of how the Fund will perform in the future.
Line Graph [Table Text Block]
Growth of 10K Chart
Table Summary
Bruce Fund
S&P 500® Index
Jun-2016
$10,000
$10,000
Jun-2017
$10,374
$11,790
Jun-2018
$10,789
$13,484
Jun-2019
$11,740
$14,889
Jun-2020
$12,088
$16,006
Jun-2021
$15,644
$22,536
Jun-2022
$14,900
$20,144
Jun-2023
$14,772
$24,091
Jun-2024
$15,262
$30,006
Jun-2025
$16,452
$34,556
Jun-2026
$21,008
$42,271
Average Annual Return [Table Text Block]

Average Annual Total Returns 

Table Summary
1 Year
5 Years
10 Years
Bruce Fund
27.69%
6.07%
7.71%
S&P 500® Index
22.32%
13.41%
15.51%

The Fund’s past performance is not a good predictor of how the Fund will perform in the future. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. For updated performance call (800) 872-7823.
No Deduction of Taxes [Text Block] The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.
AssetsNet $ 375,713,568
Holdings Count | Holding 43
Advisory Fees Paid, Amount $ 1,445,014
InvestmentCompanyPortfolioTurnover 5.00%
Additional Fund Statistics [Text Block]

Fund Statistics 

Table Summary
Net Assets
$375,713,568
Number of Portfolio Holdings
43
Advisory Fee
$1,445,014
Portfolio Turnover
5%
Holdings [Text Block]

Asset Weighting (% of total investments)

Group By Asset Type Chart
Table Summary
Value
Value
Common Stocks
91.5%
Convertible Corporate Bonds
0.0%
Money Market Funds
4.6%
U.S. Government Bonds
3.9%

Sector Weighting (% of net assets)

Group By Sector Chart
Table Summary
Value
Value
Energy
0.3%
Communications
2.9%
U.S. Treasury Obligations
3.9%
Money Market Funds
4.6%
Consumer Staples
5.4%
Materials
5.6%
Technology
7.2%
Industrials
9.5%
Financials
14.0%
Utilities
19.9%
Health Care
26.7%

Top 10 Holdings (% of net assets)

Table Summary
Holding Name
% of Net Assets
AerCap Holdings N.V.
7.0%
Allstate Corp. (The)
6.9%
AbbVie, Inc.
6.7%
Merck & Co., Inc.
6.2%
NextEra Energy, Inc.
6.1%
U-Haul Holding Co., Class B
5.5%
Vicor Corp.
4.8%
Duke Energy Corp.
4.7%
Morgan Stanley Institutional Liquidity Government Portfolio, Institutional Class
4.6%
Xcel Energy, Inc.
3.8%
Material Fund Change [Text Block]

Material Fund Changes