Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 355	$ 467	$ 1,986	$ 2,121
Less: Net income attributable to redeemable and non-redeemable noncontrolling interests	12	11	48	55
Net income attributable to Aon shareholders	343	456	1,938	2,066
Other comprehensive income, net of tax:
Change in fair value of financial instruments	8	(5)	84	6
Foreign currency translation adjustments	349	(257)	129	(29)
Postretirement benefit obligation	0	20	39	66
Total other comprehensive income (loss)	357	(242)	252	43
Less: Other comprehensive income attributable to noncontrolling interests	0	(1)	0	(1)
Total other comprehensive income (loss) attributable to Aon shareholders	357	(241)	252	44
Comprehensive income attributable to Aon shareholders	$ 700	$ 215	$ 2,190	$ 2,110