Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue
Total revenue	$ 2,368	$ 2,282	$ 4,749	$ 4,558
Expenses
Compensation and benefits	1,457	1,396	2,918	2,741
Information technology	98	99	186	182
Premises	86	89	170	171
Depreciation of fixed assets	54	41	108	79
Amortization and impairment of intangible assets	460	38	503	75
Other general expenses	331	232	639	503
Total operating expenses	2,486	1,895	4,524	3,751
Operating income	(118)	387	225	807
Interest income	8	3	10	5
Interest expense	(71)	(73)	(141)	(142)
Other income (expense)	(5)	(1)	(15)	17
Income from continuing operations before income taxes	(186)	316	79	687
Income tax expense (benefit)	(143)	43	(143)	102
Net income (loss) from continuing operations	(43)	273	222	585
Income from discontinued operations, net of tax	821	35	861	60
Net income	778	308	1,083	645
Less: Net income attributable to noncontrolling interests	9	8	23	20
Net income attributable to Aon shareholders	$ 769	$ 300	$ 1,060	$ 625
Basic net income (loss) per share attributable to Aon shareholders
Basic net income per share attributable to Aon shareholders, continuing operations (in dollars per share)	$ (0.20)	$ 0.99	$ 0.75	$ 2.10
Basic net income per share attributable to Aon shareholders, discontinued operations (in dollars per share)	3.13	0.13	3.27	0.22
Basic net income per share attributable to Aon shareholders (in dollars per share)	2.93	1.12	4.02	2.32
Diluted net income (loss) per share attributable to Aon shareholders
Net income per diluted share attributable to Aon shareholders, continuing operations (in dollars per share)	(0.20)	0.98	0.75	2.08
Net income per diluted share attributable to Aon shareholders, discontinued operations (in dollars per share)	3.13	0.13	3.24	0.22
Diluted net income per share attributable to Aon shareholders (in dollars per share)	2.93	1.11	3.99	2.30
Cash dividends per share paid on ordinary shares (in dollars per share)	$ 0.36	$ 0.33	$ 0.69	$ 0.63
Weighted average ordinary shares outstanding - basic (in shares)	262.4	268.0	263.6	269.9
Weighted average ordinary shares outstanding - diluted (in shares)	262.4	269.8	265.7	271.7