Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
Net income	$ 470	$ 355	$ 2,046	$ 1,986
Less: Net income attributable to redeemable and nonredeemable noncontrolling interests	12	12	44	48
Net income attributable to Aon shareholders	458	343	2,002	1,938
Other comprehensive income (loss), net of tax:
Change in fair value of financial instruments	(9)	8	4	84
Foreign currency translation adjustments	(91)	349	752	129
Postretirement benefit obligation	28	0	74	39
Total other comprehensive income (expense)	(72)	357	830	252
Less: Other comprehensive income attributable to noncontrolling interests	0	0	0	0
Total other comprehensive income (expense) attributable to Aon shareholders	(72)	357	830	252
Comprehensive income attributable to Aon shareholders	$ 386	$ 700	$ 2,832	$ 2,190