Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 2,628	$ 2,646	$ 1,308
Less: Net income attributable to noncontrolling interests	64	57	53
Net income attributable to Aon shareholders	2,564	2,589	1,255
Other comprehensive income (loss), net of tax:
Change in fair value of financial instruments	13	(13)	1
Foreign currency translation adjustments	276	(528)	(289)
Postretirement benefit obligation	(40)	(211)	277
Total other comprehensive income (loss)	249	(752)	(11)
Less: Other comprehensive loss attributable to noncontrolling interests	(1)	0	(1)
Total other comprehensive income (loss) attributable to Aon shareholders	250	(752)	(10)
Comprehensive income attributable to Aon shareholders	$ 2,814	$ 1,837	$ 1,245