Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Statement of Comprehensive Income [Abstract]
Net income	$ 594	$ 538	$ 1,576	$ 1,631
Less: Net income attributable to redeemable and nonredeemable noncontrolling interests	15	14	32	36
Net income attributable to Aon shareholders	579	524	1,544	1,595
Other comprehensive income (loss), net of tax:
Change in fair value of financial instruments	10	1	13	76
Foreign currency translation adjustments	604	(88)	843	(220)
Postretirement benefit obligation	(1)	13	46	39
Total other comprehensive income (loss)	613	(74)	902	(105)
Less: Other comprehensive income attributable to noncontrolling interests	0	0	0	0
Total other comprehensive income (loss) attributable to Aon shareholders	613	(74)	902	(105)
Comprehensive income attributable to Aon shareholders	$ 1,192	$ 450	$ 2,446	$ 1,490