v3.26.1
Shareholder Report
 6 Months Ended
May 31, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name THOMPSON IM FUNDS, INC.
Entity Central Index Key 0000795264
Entity Investment Company Type N-1A
Document Period End Date May 31, 2026
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Thompson LargeCap Fund  
Shareholder Report [Line Items]  
Fund Name Thompson LargeCap Fund
Class Name Thompson LargeCap Fund
Trading Symbol THPGX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Thompson LargeCap Fund for the period of December 1, 2025 to May 31, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at http://www.thompsonim.com/forms/index.html. You can also request this information by contacting us at 1-800-999-0887 or thompsonimfunds@usbank.com.
Additional Information Phone Number 1-800-999-0887
Additional Information Email thompsonimfunds@usbank.com
Additional Information Website http://www.thompsonim.com/forms/index.html
Expenses [Text Block]

  WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)  
         
    Costs of a $10,000 Costs paid as a percentage of    
    Fund Name investment a $10,000 investment^    
    Thompson LargeCap Fund $53 0.99%    
         

 

^ Annualized 

 
Expenses Paid, Amount $ 53
Expense Ratio, Percent 0.99% [1]
Net Assets $ 223,233,039
Holdings Count | Holding 80
Investment Company, Portfolio Turnover 19.00%
Additional Fund Statistics [Text Block]

  KEY FUND STATISTICS (as of May 31, 2026)  
  Net Assets $223,233,039  
  Number of Holdings 80  
  Portfolio Turnover 19%  
       
Holdings [Text Block]
Sector Weightings (%)
Information Technology 27.0%
Health Care 17.4%
Financials 17.3%
Communication Services 11.3%
Consumer Staples 8.3%
Consumer Discretionary 5.6%
Industrials 5.0%
Energy 2.6%
Materials 2.0%
Net Other Assets & Liabilities 3.5%
Largest Holdings [Text Block]
Top Holdings (%)
Alphabet Inc. Class A 6.3%
Microsoft Corp. 4.2%
Apple Inc. 3.1%
UnitedHealth Group Inc. 2.5%
Citigroup Inc. 2.5%
Qualcomm Inc. 2.1%
NXP Semiconductors N.V. 2.1%
LKQ Corp. 2.0%
Pfizer Inc. 1.9%
Warner Bros. Discovery, Inc. 1.8%
Updated Prospectus Phone Number 1-800-999-0887
Updated Prospectus Email Address thompsonimfunds@usbank.com
Updated Prospectus Web Address http://www.thompsonim.com/forms/index.html
Thompson MidCap Fund  
Shareholder Report [Line Items]  
Fund Name Thompson MidCap Fund
Class Name Thompson MidCap Fund
Trading Symbol THPMX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Thompson MidCap Fund for the period of December 1, 2025 to May 31, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at http://www.thompsonim.com/forms/index.html. You can also request this information by contacting us at 1-800-999-0887 or thompsonimfunds@usbank.com.
Additional Information Phone Number 1-800-999-0887
Additional Information Email thompsonimfunds@usbank.com
Additional Information Website http://www.thompsonim.com/forms/index.html
Expenses [Text Block]

  WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)  
         
    Costs of a $10,000 Costs paid as a percentage of    
    Fund Name investment a $10,000 investment^    
    Thompson MidCap Fund $62 1.15%    
         

 

^ Annualized 
Expenses Paid, Amount $ 62
Expense Ratio, Percent 1.15% [2]
Net Assets $ 62,087,946
Holdings Count | Holding 78
Investment Company, Portfolio Turnover 22.00%
Additional Fund Statistics [Text Block]

  KEY FUND STATISTICS (as of May 31, 2026)  
  Net Assets $62,087,946  
  Number of Holdings 78  
  Portfolio Turnover 22%  
       
Holdings [Text Block]
Sector Weightings (%)
Financials 17.9%
Health Care 17.7%
Information Technology 15.2%
Industrials 12.8%
Consumer Discretionary 8.1%
Real Estate 7.7%
Consumer Staples 6.9%
Utilities 4.3%
Materials 4.1%
Net Other Assets & Liabilities 5.3%
Largest Holdings [Text Block]
Top Holdings (%)
Viatris Inc. 2.9%
AMN Healthcare Services, Inc. 2.5%
Neurocrine Biosciences, Inc. 2.5%
Concentrix Corp. 2.3%
Kornit Digital Ltd. 2.3%
Jazz Pharmaceuticals PLC 2.2%
NXP Semiconductors N.V. 2.1%
LKQ Corp. 2.0%
Flagstar Bank N.A. 2.0%
Okta, Inc. 2.0%
Updated Prospectus Phone Number 1-800-999-0887
Updated Prospectus Email Address thompsonimfunds@usbank.com
Updated Prospectus Web Address http://www.thompsonim.com/forms/index.html
Thompson Bond Fund  
Shareholder Report [Line Items]  
Fund Name Thompson Bond Fund
Class Name Thompson Bond Fund
Trading Symbol THOPX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Thompson Bond Fund for the period of December 1, 2025 to May 31, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at http://www.thompsonim.com/forms/index.html. You can also request this information by contacting us at 1-800-999-0887 or thompsonimfunds@usbank.com.
Additional Information Phone Number 1-800-999-0887
Additional Information Email thompsonimfunds@usbank.com
Additional Information Website http://www.thompsonim.com/forms/index.html
Expenses [Text Block]

     
  WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)  
         
      Costs of a $10,000 Costs paid as a percentage of    
    Fund Name investment a $10,000 investment^    
    Thompson Bond Fund $36 0.72%    
         

 

^Annualized

Expenses Paid, Amount $ 36
Expense Ratio, Percent 0.72% [3]
Net Assets $ 1,934,428,615
Holdings Count | Holding 527
Investment Company, Portfolio Turnover 10.00%
Additional Fund Statistics [Text Block]

  KEY FUND STATISTICS (as of May 31, 2026)  
  Net Assets $1,934,428,615  
  Number of Holdings 527  
  Portfolio Turnover 10%  
  Average Credit Quality+ BBB  
  Effective Duration 3.25 yrs  
       
Holdings [Text Block]
Asset Allocation (%)
Corporate Bonds 73.2%
Commercial Mortgage-Backed Securities 8.2%
Asset-Backed Securities 7.7%
U.S. Government & Agency Securities 4.8%
Residential Mortgage-Backed Securities 2.6%
U.S. Government Agency Mortgage-Backed Securities 1.8%
Net Other Assets & Liabilities1.7%
 
Credit Rating Description+ (%)
AAA 3.0%
AA 7.8%
A 12.3%
BBB 61.9%
BB and Below 12.1%
Not Rated 1.2%
Net Other Assets & Liabilities 1.7%

+Ratings provided by Standard & Poor’s, Moody’s, and Fitch. When ratings are available from multiple rating agencies, a conservative methodology is to be adopted: For cases where there are three distinct ratings available, use the middle-quality rating (dropping the highest and lowest ratings); if two different ratings are available, use the lower rating; if only one agency rates a holding, then use that rating. For certain securities that are not rated by any of these three agencies, credit ratings from other agencies may be used. For cases where there is not a rating available from any agency, the holding is classified as Not Rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest).
Credit Quality Explanation [Text Block] Ratings provided by Standard & Poor’s, Moody’s, and Fitch. When ratings are available from multiple rating agencies, a conservative methodology is to be adopted: For cases where there are three distinct ratings available, use the middle-quality rating (dropping the highest and lowest ratings); if two different ratings are available, use the lower rating; if only one agency rates a holding, then use that rating. For certain securities that are not rated by any of these three agencies, credit ratings from other agencies may be used. For cases where there is not a rating available from any agency, the holding is classified as Not Rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest).
Largest Holdings [Text Block]
Top 10 Issuers (%)
U.S. Treasury Bills 3.2%
Lincoln National Corp. 2.3%
Brean Asset Backed Securities Trust 2.1%
Federal Home Loan Banks 1.5%
JPMBB Commercial Mortgage Securities Trust 1.2%
Ginnie Mae REMIC Trust 1.2%
COMM Mortgage Trust 1.1%
WFRBS Commercial Mortgage Trust 1.1%
TransCanada PipeLines Ltd. 0.8%
Morgan Stanley Bank of America Merrill Lynch Trust 0.8%
Updated Prospectus Phone Number 1-800-999-0887
Updated Prospectus Email Address thompsonimfunds@usbank.com
Updated Prospectus Web Address http://www.thompsonim.com/forms/index.html
[1] Annualized 
[2] Annualized 
[3] Annualized