Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 2,720	$ 2,628	$ 2,646
Less: Net income attributable to redeemable and nonredeemable noncontrolling interests	66	64	57
Net income attributable to Aon shareholders	2,654	2,564	2,589
Other comprehensive income (loss), net of tax:
Change in fair value of financial instruments	72	13	(13)
Foreign currency translation adjustments	(467)	276	(528)
Postretirement benefit obligation	23	(40)	(211)
Total other comprehensive income (loss)	(372)	249	(752)
Less: Other comprehensive loss attributable to noncontrolling interests	0	(1)	0
Total other comprehensive income (loss) attributable to Aon shareholders	(372)	250	(752)
Comprehensive income attributable to Aon shareholders	$ 2,282	$ 2,814	$ 1,837