| Form N-CSR Cover | 6 Months Ended |
| May 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS/A |
| 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, 2024 |
| Shareholder Report | 6 Months Ended |
| May 31, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS/A |
| 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, 2024 |
| 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, 2023, to May 31, 2024. |
| 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 1-800-999-0887 thompsonimfunds usbank.com |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-999-0887 |
| 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 |
| Expenses Paid, Amount | $ 53 |
| Expense Ratio, Percent | 0.99% |
| Net Assets | $ 173,772,405 |
| Holdings Count | Holding | 74 |
| Investment Company, Portfolio Turnover | 14% |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Net Assets $ 173,772,405 Number of Holdings 74 Portfolio Turnover 14 |
| Holdings [Text Block] | Top Sectors (%) Information Technology 23.7 Financials 19.3 Health Care 17.8 Communication Services 13.1 Consumer Staples 7.0 Consumer Discretionary 6.8 Industrials 4.6 Energy 3.7 Materials 2.5 Cash & Other 1.5 |
| Largest Holdings [Text Block] | Top Holdings (%) Alphabet, Inc. Class A 5.1 Microsoft Corp. 4.4 Apple, Inc. 2.7 Qualcomm, Inc. 2.5 Citigroup, Inc. 2.3 Meta Platforms, Inc. Class A 2.2 Pfizer, Inc. 2.1 Visa, Inc. Class A 2.1 Warner Bros Discovery, Inc. 2.0 PayPal Holdings, Inc. 2.0 |
| 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, 2023, to May 31, 2024. |
| 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 1-800-999-0887 thompsonimfunds usbank.com |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-999-0887 |
| 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 $ 60 1.15 |
| Expenses Paid, Amount | $ 60 |
| Expense Ratio, Percent | 1.15% |
| Net Assets | $ 54,147,064 |
| Holdings Count | Holding | 83 |
| Investment Company, Portfolio Turnover | 16% |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Net Assets $ 54,147,064 Number of Holdings 83 Portfolio Turnover 16 |
| Holdings [Text Block] | Top Sectors (%) Financials 19.7 Industrials 16.5 Information Technology 14.0 Health Care 12.9 Consumer Discretionary 10.5 Real Estate 6.5 Communication Services 5.1 Consumer Staples 4.7 Materials 4.6 Cash & Other 5.5 |
| Largest Holdings [Text Block] | Top Holdings (%) Warner Bros Discovery, Inc. 2.4 NXP Semiconductors NV 2.2 Calix, Inc. 2.2 Discover Financial Services 2.2 Chewy, Inc. Class A 2.1 Bread Financial Holdings, Inc. 2.0 O-I Glass, Inc. 2.0 Neurocrine Biosciences, Inc. 2.0 Kornit Digital Ltd. 2.0 Viatris, Inc. 2.0 |
| 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, 2023, to May 31, 2024. |
| 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 1-800-999-0887 thompsonimfunds usbank.com |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-999-0887 |
| 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 $ 39 0.75 |
| Expenses Paid, Amount | $ 39 |
| Expense Ratio, Percent | 0.75% |
| Net Assets | $ 1,301,597,964 |
| Holdings Count | Holding | 357 |
| Investment Company, Portfolio Turnover | 11% |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Net Assets $ 1,301,597,964 Number of Holdings 357 Portfolio Turnover 11 Average Credit Quality BBB Effective Duration 1.79 yrs |
| Holdings [Text Block] | Asset Allocation (%) Corporate Bonds 60.4 Commercial Mortgage-Backed Securities 16.0 Asset-Backed Securities 15.2 U.S. Government & Agency Securities 3.9 U.S. Government Agency Mortgage-Backed Securities 2.7 Net Other Assets & Liabilities 1.8 Credit Rating Description (%) AAA AAA Rating [Member] 0.3 AA AA Rating [Member] 7.8 A A Rating [Member] 14.8 BBB BBB Rating [Member] 58.3 BB and Below 15.9 Not Rated 1.1 Other Net Assets and Liabilities 1.8 |
| Largest Holdings [Text Block] | Top 10 Issuers (%) Lincoln National Corp. 3.4 United States Treasury Note/Bond 2.3 JPMBB Commercial Mortgage Securities Trust 2.2 Labrador Aviation Finance Ltd. 2.0 Morgan Stanley Bank of America Merrill Lynch Trust 1.9 Commercial Mortgage Pass Through Certificates 1.9 Well Fargo Commercial Mortgage Trust 1.9 Coinstar Funding LLC 1.8 Reinsurance Group of America, Inc. 1.7 TransCanada PipeLines Ltd. 1.6 |
| Updated Prospectus Web Address | http://www.thompsonim.com/forms/index.html |
| Shareholder Report, Holdings (Details) | May 31, 2024 |
| Thompson LargeCap Fund | Alphabet, Inc. Class A [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| Thompson LargeCap Fund | Microsoft Corp. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.40% |
| Thompson LargeCap Fund | Apple, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Thompson LargeCap Fund | Qualcomm, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| Thompson LargeCap Fund | Citigroup, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Thompson LargeCap Fund | Meta Platforms, Inc. Class A [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Thompson LargeCap Fund | Pfizer, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Thompson LargeCap Fund | Visa, Inc. Class A [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Thompson LargeCap Fund | Warner Bros Discovery, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson LargeCap Fund | PayPal Holdings, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson LargeCap Fund | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.70% |
| Thompson LargeCap Fund | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.30% |
| Thompson LargeCap Fund | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.80% |
| Thompson LargeCap Fund | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Thompson LargeCap Fund | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7% |
| Thompson LargeCap Fund | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.80% |
| Thompson LargeCap Fund | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Thompson LargeCap Fund | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| Thompson LargeCap Fund | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| Thompson LargeCap Fund | Cash & Other [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Thompson MidCap Fund | Warner Bros Discovery, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Thompson MidCap Fund | NXP Semiconductors NV [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Thompson MidCap Fund | Calix, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Thompson MidCap Fund | Discover Financial Services [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Thompson MidCap Fund | Chewy, Inc. Class A [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Thompson MidCap Fund | Bread Financial Holdings, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson MidCap Fund | O-I Glass, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson MidCap Fund | Neurocrine Biosciences, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson MidCap Fund | Kornit Digital Ltd. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson MidCap Fund | Viatris, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson MidCap Fund | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14% |
| Thompson MidCap Fund | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.70% |
| Thompson MidCap Fund | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.90% |
| Thompson MidCap Fund | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| Thompson MidCap Fund | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Thompson MidCap Fund | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.50% |
| Thompson MidCap Fund | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.50% |
| Thompson MidCap Fund | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Thompson MidCap Fund | Cash & Other [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Thompson MidCap Fund | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Thompson Bond Fund | Lincoln National Corp. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Thompson Bond Fund | United States Treasury Note/Bond [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Thompson Bond Fund | JPMBB Commercial Mortgage Securities Trust [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Thompson Bond Fund | Labrador Aviation Finance Ltd. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Thompson Bond Fund | Morgan Stanley Bank of America Merrill Lynch Trust [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Thompson Bond Fund | Commercial Mortgage Pass Through Certificates [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Thompson Bond Fund | Well Fargo Commercial Mortgage Trust [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Thompson Bond Fund | Coinstar Funding LLC [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Thompson Bond Fund | Reinsurance Group of America, Inc. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Thompson Bond Fund | TransCanada PipeLines Ltd. [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Thompson Bond Fund | AAA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Thompson Bond Fund | AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.80% |
| Thompson Bond Fund | A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.80% |
| Thompson Bond Fund | BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 58.30% |
| Thompson Bond Fund | BB and Below Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.90% |
| Thompson Bond Fund | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Thompson Bond Fund | Other Net Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Thompson Bond Fund | Corporate Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 60.40% |
| Thompson Bond Fund | Asset-Backed Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.20% |
| Thompson Bond Fund | Commercial Mortgage-Backed Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16% |
| Thompson Bond Fund | U.S. Government & Agency Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Thompson Bond Fund | U.S. Government Agency Mortgage-Backed Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Thompson Bond Fund | Net Other Assets & Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
