Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 2,646	$ 1,308	$ 2,018
Less: Net income attributable to noncontrolling interests	57	53	49
Net income attributable to Aon shareholders	2,589	1,255	1,969
Other comprehensive income (loss), net of tax:
Change in fair value of financial instruments	(13)	1	13
Foreign currency translation adjustments	(528)	(289)	263
Postretirement benefit obligation	(211)	277	(101)
Total other comprehensive income (loss)	(752)	(11)	175
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	(1)	3
Total other comprehensive income (loss) attributable to Aon shareholders	(752)	(10)	172
Comprehensive income attributable to Aon shareholders	$ 1,837	$ 1,245	$ 2,141