Operating expenses - Additional Information (Details) - Licensing and collaboration agreement with CTTQ - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disclosure of attribution of expenses by nature to their function [line items]
Withholding tax (as a percent)	10.00%
Withholding taxes	€ 1.0	€ 1.0	€ 0.5

The amount of withholding tax expense (income) relating to changes in deferred tax liabilities and deferred tax assets.

No definition available.

Name:	iva_WithholdingTaxExpenseIncomeRecognizedInProfitOrLoss
Namespace Prefix:	iva_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration