Accelerating Aon United Program - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2025	Sep. 30, 2024
Restructuring Cost and Reserve [Line Items]
Charges	$ 32	$ 69		$ 236	$ 320
Accelerating Aon United Program
Restructuring Cost and Reserve [Line Items]
Restructuring plan, period			3 years
Expected cost	1,000			1,000
Expected cost, cash charges	900			900
Expected cost, non-cash charges	100			100
Charges	32	$ 69		236	$ 320
Accelerating Aon United Program \| Risk Capital
Restructuring Cost and Reserve [Line Items]
Expected cost	230			230
Accelerating Aon United Program \| Human Capital
Restructuring Cost and Reserve [Line Items]
Expected cost	$ 60			$ 60

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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- Definition

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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Aon plc 10-Q