Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue
Total revenue	$ 2,340	$ 2,201	$ 7,089	$ 6,759
Expenses
Compensation and benefits	1,419	1,300	4,337	4,041
Information technology	109	99	295	281
Premises	89	86	259	257
Depreciation of fixed assets	40	39	148	118
Amortization and impairment of intangible assets	101	42	604	117
Other general expenses	317	267	956	770
Total operating expenses	2,075	1,833	6,599	5,584
Operating income	265	368	490	1,175
Interest income	10	1	20	6
Interest expense	(70)	(70)	(211)	(212)
Other income (expense)	(5)	10	(20)	27
Income from continuing operations before income taxes	200	309	279	996
Income tax expense (benefit)	4	25	(139)	127
Net income from continuing operations	196	284	418	869
Income (loss) from discontinued operations, net of tax	(4)	42	857	102
Net income	192	326	1,275	971
Less: Net income attributable to noncontrolling interests	7	7	30	27
Net income attributable to Aon shareholders	$ 185	$ 319	$ 1,245	$ 944
Basic net income (loss) per share attributable to Aon shareholders
Basic net income (loss) per share attributable to Aon shareholders, continuing operations (in dollars per share)	$ 0.74	$ 1.03	$ 1.49	$ 3.13
Basic net income (loss) per share attributable to Aon shareholders, discontinued operations (in dollars per share)	(0.02)	0.16	3.28	0.38
Basic net income (loss) per share attributable to Aon shareholders (in dollars per share)	0.72	1.19	4.77	3.51
Diluted net income (loss) per share attributable to Aon shareholders
Diluted net income (loss) per share attributable to Aon shareholders, continuing operations (in dollars per share)	0.73	1.03	1.48	3.11
Diluted net income (loss) per share attributable to Aon shareholders, discontinued operations (in dollars per share)	(0.01)	0.15	3.26	0.37
Diluted net income (loss) per share attributable to Aon shareholders (in dollars per share)	0.72	1.18	4.74	3.48
Cash dividends per share paid on ordinary shares (in dollars per share)	$ 0.36	$ 0.33	$ 1.05	$ 0.96
Weighted average ordinary shares outstanding - basic (in shares)	255.6	267.5	260.9	269.1
Weighted average ordinary shares outstanding - diluted (in shares)	257.3	269.6	262.9	271.0