Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 1,079	$ 1,048
Less: Net income attributable to noncontrolling interests	29	25
Net income attributable to Aon shareholders	1,050	1,023
Other comprehensive income, net of tax:
Change in fair value of financial instruments	3	1
Foreign currency translation adjustments	54	(7)
Postretirement benefit obligation	22	33
Total other comprehensive income	79	27
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	(1)
Total other comprehensive income attributable to Aon shareholders	79	28
Comprehensive income attributable to Aon shareholders	$ 1,129	$ 1,051