Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue
Total revenue	$ 2,886	$ 2,497	$ 6,411	$ 5,716
Expenses
Compensation and benefits	1,628	1,361	3,347	2,883
Information technology	115	107	229	218
Premises	76	74	153	147
Depreciation of fixed assets	41	41	82	82
Amortization of intangible assets	36	58	76	155
Other general expense	318	262	607	604
Total operating expenses	2,214	1,903	4,494	4,089
Operating income	672	594	1,917	1,627
Interest income	3	0	6	2
Interest expense	(78)	(89)	(157)	(172)
Other income (expense)	(1)	(9)	(3)	19
Income before income taxes	596	496	1,763	1,476
Income tax expense	203	85	437	274
Net income	393	411	1,326	1,202
Less: Net income attributable to noncontrolling interests	14	13	34	32
Net income attributable to Aon shareholders	$ 379	$ 398	$ 1,292	$ 1,170
Basic net income per share attributable to Aon shareholders (in dollars per share)	$ 1.67	$ 1.71	$ 5.69	$ 5.02
Diluted net income per share attributable to Aon shareholders (in dollars per share)	$ 1.66	$ 1.70	$ 5.66	$ 5.00
Weighted average ordinary shares outstanding - basic (in shares)	227.0	232.7	227.0	233.0
Weighted average ordinary shares outstanding - diluted (in shares)	228.0	233.6	228.1	234.1