Shareholders' Equity - Distributable Profits (Details) - USD ($) $ in Millions	Dec. 31, 2021	Jul. 26, 2021	Dec. 31, 2020
Equity [Abstract]
Distributable profits approved amount		$ 34,000
Distributable reserves available amount	$ 32,700		$ 200

Represents the amount of distributable reserves maintained by the entity.

No definition available.

Name:	aon_DistributableReservesAvailableAmount
Namespace Prefix:	aon_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant