The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 7
-IssueDate 2025-01-01
-Paragraph 45
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2025-en-r&anchor=para_45&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2025-01-01
-Paragraph B13
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2025-en-r&anchor=para_B13_a&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 169
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_169&doctype=Standard
-URIDate 2025-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 169
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_169&doctype=Standard
-URIDate 2025-03-27

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_i&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_CashAndCashEquivalents
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of exchange differences recognised in profit or loss that arise from foreign currency transactions, excluding those arising on financial instruments measured at fair value through profit or loss in accordance with IFRS 9. [Refer: At fair value [member]; Classes of financial instruments [domain]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 21
-IssueDate 2025-01-01
-Paragraph 52
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=21&code=ifrs-tx-2025-en-r&anchor=para_52_a&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 218
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_218_a&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 218
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_218_a&doctype=Standard
-URIDate 2025-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 35
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_35&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 13
-IssueDate 2025-01-01
-Paragraph 93
-Subparagraph h
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2025-en-r&anchor=para_93_h_ii&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_IncreaseDecreaseInFairValueMeasurementDueToReasonablyPossibleDecreaseInUnobservableInputRecognisedInProfitOrLossBeforeTaxLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- References

+ Details

Name:	ifrs-full_IncreaseDecreaseInFairValueMeasurementDueToReasonablyPossibleIncreaseInUnobservableInputRecognisedInProfitOrLossBeforeTaxLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount that best represents the maximum exposure to credit risk without taking into account any collateral held or other credit enhancements (for example, netting agreements that do not qualify for offset in accordance with IAS 32). [Refer: Credit risk [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2025-01-01
-Paragraph 35K
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2025-en-r&anchor=para_35K_a&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_MaximumExposureToCreditRisk
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of financial assets that the entity does not separately disclose in the same statement or note. [Refer: Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph d
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_d&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_OtherFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of a reasonably possible decrease in an unobservable input used in fair value measurement of liabilities.

+ References

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleDecreaseInUnobservableInputLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of a reasonably possible increase in an unobservable input used in fair value measurement of liabilities.

+ References

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleIncreaseInUnobservableInputLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount due from customers for goods and services sold.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph B9
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_B9_b&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 78
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_78_b&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_TradeReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Bonds and short-term deposits.

+ References

No definition available.

+ Details

Name:	imtx_BondsAndShortTermDeposits
Namespace Prefix:	imtx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financial risk management objectives and policies.

+ References

No definition available.

+ Details

Name:	imtx_FinancialRiskManagementObjectivesAndPoliciesLineItems
Namespace Prefix:	imtx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of cash and cash equivalents held in domicile.

+ References

No definition available.

+ Details

Name:	imtx_PercentageOfCashAndCashEquivalentsHeldInDomicile
Namespace Prefix:	imtx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of Reasonably Possible Decrease In Foreign Currency Risk.

+ References

No definition available.

+ Details

Name:	imtx_PercentageOfReasonablyPossibleDecreaseInForeignCurrencyRisk
Namespace Prefix:	imtx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of Reasonably Possible Increase In Foreign Currency Risk.

+ References

No definition available.

+ Details

Name:	imtx_PercentageOfReasonablyPossibleIncreaseInForeignCurrencyRisk
Namespace Prefix:	imtx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	ifrs-full_UnobservableInputsAxis=ifrs-full_HistoricalVolatilityForSharesMeasurementInputMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BusinessCombinationsAxis=imtx_AryaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=ifrs-full_WarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_UnobservableInputsAxis=imtx_ForeignExchangeRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CreditRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CurrencyRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=imtx_DeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_EUR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_USD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Financial Risk Management Objectives and Policies - Additional Information (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financial Risk Management Objectives And Policies [Line Items]
Cash and cash equivalents	€ 345,918	€ 236,748	€ 218,472	€ 148,519
Trade receivables	€ 6,100	€ 5,900
Historical volatility for shares, measurement input [Member] \| ARYA [Member] \| Warrants [Member]
Financial Risk Management Objectives And Policies [Line Items]
Percentage of reasonable possible increase in unobservable inputs	10.00%
Percentage of resonably possible decrease in unobservable inputs	10.00%
Increase decrease in fair value measurement due to a reasonably possible increase in unobservable input recognized in profit or loss before tax liabilities	€ 200
Foreign Exchange Rates [Member] \| ARYA [Member] \| Warrants [Member]
Financial Risk Management Objectives And Policies [Line Items]
Percentage Of Reasonably Possible Decrease In Foreign Currency Risk	10.00%	10.00%
Increase decrease in fair value measurement due to a reasonably possible increase in unobservable input recognized in profit or loss before tax liabilities	€ 0	€ 200
Increase decrease in fair value measurement due to a reasonably possible decrease in unobservable input recognized in profit or loss before tax liabilities		200
Credit risk [Member]
Financial Risk Management Objectives And Policies [Line Items]
Maximum exposure to credit risk	475,400	610,300
Cash and cash equivalents	345,900	236,700
Other financial assets	123,400	367,700
Currency risk [Member]
Financial Risk Management Objectives And Policies [Line Items]
Cash and cash equivalents	€ 345,900
Currency risk [Member] \| Germany [Member]
Financial Risk Management Objectives And Policies [Line Items]
Percentage of cash and cash equivalents held in domicile	95.00%
Currency risk [Member] \| Bottom of range [Member]
Financial Risk Management Objectives And Policies [Line Items]
Foreign exchange gain (loss)	€ 25,200	31,300
Currency risk [Member] \| Top of range [Member]
Financial Risk Management Objectives And Policies [Line Items]
Foreign exchange gain (loss)	30,800	€ 38,300
Currency risk [Member] \| Euro [Member]
Financial Risk Management Objectives And Policies [Line Items]
Bonds and short-term deposits	€ 45,600
Currency risk [Member] \| Euro [Member] \| Germany [Member]
Financial Risk Management Objectives And Policies [Line Items]
Percentage of cash and cash equivalents held in domicile	39.00%
Currency risk [Member] \| US [Member]
Financial Risk Management Objectives And Policies [Line Items]
Percentage Of Reasonably Possible Increase In Foreign Currency Risk	10.00%	10.00%
Bonds and short-term deposits	€ 77,800
Currency risk [Member] \| US [Member] \| Germany [Member]
Financial Risk Management Objectives And Policies [Line Items]
Percentage of cash and cash equivalents held in domicile	61.00%