Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Total revenue	$ 11,066	$ 11,013	$ 10,770
Expenses
Compensation and benefits	5,905	6,054	6,103
Information technology	444	494	484
Premises	291	339	370
Depreciation of fixed assets	167	172	176
Amortization and impairment of intangible assets	246	392	593
Other general expense	1,232	1,393	1,500
Total operating expenses	8,285	8,844	9,226
Operating income	2,781	2,169	1,544
Interest income	6	8	5
Interest expense	(334)	(307)	(278)
Other income (expense)	12	1	(25)
Income from continuing operations before income taxes	2,465	1,871	1,246
Income tax expense	448	297	146
Net income from continuing operations	2,017	1,574	1,100
Net income (loss) from discontinued operations	1	(1)	74
Net income	2,018	1,573	1,174
Less: Net income attributable to noncontrolling interests	49	41	40
Net income attributable to Aon shareholders	$ 1,969	$ 1,532	$ 1,134
Basic net income per share attributable to Aon shareholders
Continuing operations (in dollars per share)	$ 8.49	$ 6.42	$ 4.32
Discontinued operations (in dollars per share)	0	0	0.30
Net income (in dollars per share)	8.49	6.42	4.62
Diluted net income per share attributable to Aon shareholders
Continuing operations (in dollars per share)	8.45	6.37	4.29
Discontinued operations (in dollars per share)	0	0	0.30
Net income (in dollars per share)	$ 8.45	$ 6.37	$ 4.59
Weighted average ordinary shares outstanding - basic (in shares)	231.9	238.6	245.2
Weighted average ordinary shares outstanding - diluted (in shares)	233.1	240.6	247.0