Summary of significant accounting policies - Schedule of Finite-Lived Intangible Assets (Details)	Sep. 30, 2025
Patient database
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	7 years
Technology assets
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Minimum \| Customer relationships
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	8 years
Minimum \| Order backlog
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Maximum \| Customer relationships
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	23 years
Maximum \| Order backlog
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

ICON PLC 6-K