Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Mar. 31, 2019
Entity Registrant Name	dei_EntityRegistrantName	THOMPSON IM FUNDS INC
Entity Central Index Key	dei_EntityCentralIndexKey	0000795264
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Mar. 28, 2019
Document Effective Date	dei_DocumentEffectiveDate	Mar. 31, 2019
Prospectus Date	rr_ProspectusDate	Mar. 31, 2019
Thompson LargeCap Fund (Prospectus Summary) \| Thompson LargeCap Fund \| Thompson LargeCap Fund
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	thpgx
Thompson MidCap Fund (Prospectus Summary) \| Thompson MidCap Fund \| Thompson MidCap Fund
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	thpmx
Thompson Bond Fund (Prospectus Summary) \| Thompson Bond Fund \| Thompson Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	thopx

If the value is true, then the document is an amendment to previously-filed/accepted document.

No definition available.

Name:	dei_AmendmentFlag
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

The date the document was made available and submitted, in CCYY-MM-DD format. The date of submission, date of acceptance by the recipient, and the document effective date are all potentially different.

+ References

No definition available.

+ Details

Name:	dei_DocumentCreationDate
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The date when a document, upon receipt and acceptance, becomes officially effective, in CCYY-MM-DD format. Usually it is a system-assigned date time value, but it may be declared by the submitter in some cases.

+ References

No definition available.

+ Details

Name:	dei_DocumentEffectiveDate
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.

+ References

No definition available.

+ Details

Name:	dei_DocumentPeriodEndDate
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word "Other".

+ References

No definition available.

+ Details

Name:	dei_DocumentType
Namespace Prefix:	dei_
Data Type:	dei:submissionTypeItemType
Balance Type:	na
Period Type:	duration

- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12b
-Subsection 1

+ Details

Name:	dei_EntityCentralIndexKey
Namespace Prefix:	dei_
Data Type:	dei:centralIndexKeyItemType
Balance Type:	na
Period Type:	duration

- Definition

The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12b
-Subsection 1

+ Details

Name:	dei_EntityRegistrantName
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Trading symbol of an instrument as listed on an exchange.

+ References

No definition available.

+ Details

Name:	dei_TradingSymbol
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

- Definition

The date of the prospectus.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 1
-Subsection a
-Paragraph 3

+ Details

Name:	rr_ProspectusDate
Namespace Prefix:	rr_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	rr_RiskReturnAbstract
Namespace Prefix:	rr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_DocumentInformationDocumentAxis=cik0000795264_S000002451SummaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cik0000795264_S000002451Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	rr_ProspectusShareClassAxis=cik0000795264_C000006581Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_DocumentInformationDocumentAxis=cik0000795264_S000021538SummaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cik0000795264_S000021538Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	rr_ProspectusShareClassAxis=cik0000795264_C000061640Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_DocumentInformationDocumentAxis=cik0000795264_S000002452SummaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cik0000795264_S000002452Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	rr_ProspectusShareClassAxis=cik0000795264_C000006582Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: