Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 538	$ 575	$ 1,631	$ 1,654
Less: Net income attributable to redeemable and non-redeemable noncontrolling interests	14	15	36	44
Net income attributable to Aon shareholders	524	560	1,595	1,610
Other comprehensive income, net of tax:
Change in fair value of financial instruments	1	8	76	11
Foreign currency translation adjustments	(88)	174	(220)	228
Postretirement benefit obligation	13	24	39	46
Total other comprehensive income (loss)	(74)	206	(105)	285
Less: Other comprehensive income attributable to noncontrolling interests	0	0	0	0
Total other comprehensive income (loss) attributable to Aon shareholders	(74)	206	(105)	285
Comprehensive income attributable to Aon shareholders	$ 450	$ 766	$ 1,490	$ 1,895