Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 575	$ 514	$ 1,654	$ 1,562
Less: Net income attributable to noncontrolling interests	15	13	44	38
Net income attributable to Aon shareholders	560	501	1,610	1,524
Other comprehensive income, net of tax:
Change in fair value of financial instruments	8	(9)	11	(8)
Foreign currency translation adjustments	174	(436)	228	(443)
Postretirement benefit obligation	24	28	46	61
Total other comprehensive income (loss)	206	(417)	285	(390)
Less: Other comprehensive loss attributable to noncontrolling interests	0	0	0	(1)
Total other comprehensive income (loss) attributable to Aon shareholders	206	(417)	285	(389)
Comprehensive income attributable to Aon shareholders	$ 766	$ 84	$ 1,895	$ 1,135