Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 1,093	$ 1,079
Less: Net income attributable to noncontrolling interests	22	29
Net income attributable to Aon shareholders	1,071	1,050
Other comprehensive income, net of tax:
Change in fair value of financial instruments	75	3
Foreign currency translation adjustments	(132)	54
Postretirement benefit obligation	26	22
Total other comprehensive income (loss)	(31)	79
Less: Other comprehensive income attributable to noncontrolling interests	0	0
Total other comprehensive income (loss) attributable to Aon shareholders	(31)	79
Comprehensive income attributable to Aon shareholders	$ 1,040	$ 1,129