Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue
Total revenue	$ 2,561	$ 2,368	$ 5,651	$ 4,749
Expenses
Compensation and benefits	1,494	1,466	3,110	2,935
Information technology	123	98	238	186
Premises	96	86	189	170
Depreciation of fixed assets	47	54	86	108
Amortization and impairment of intangible assets	282	460	392	503
Other general expenses	535	331	853	639
Total operating expenses	2,577	2,495	4,868	4,541
Operating income (loss)	(16)	(127)	783	208
Interest income	1	8	5	10
Interest expense	(69)	(71)	(139)	(141)
Other income (expense)	(3)	4	(18)	2
Income (loss) from continuing operations before income taxes	(87)	(186)	631	79
Income tax benefit	(144)	(143)	(30)	(143)
Net income (loss) from continuing operations	57	(43)	661	222
Net income from discontinued operations	1	821	7	861
Net income	58	778	668	1,083
Less: Net income attributable to noncontrolling interests	10	9	26	23
Net income attributable to Aon shareholders	$ 48	$ 769	$ 642	$ 1,060
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)	$ 0.19	$ (0.20)	$ 2.57	$ 0.75
Basic net income (loss) per share attributable to Aon shareholders, discontinued operations (in dollars per share)	0.01	3.13	0.03	3.27
Basic net income (loss) per share attributable to Aon shareholders (in dollars per share)	0.20	2.93	2.60	4.02
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)	0.19	(0.20)	2.55	0.75
Diluted net income (loss) per share attributable to Aon shareholders, discontinued operations (in dollars per share)	0.00	3.13	0.03	3.24
Diluted net income (loss) per share attributable to Aon shareholders (in dollars per share)	0.19	2.93	2.58	3.99
Cash dividends per share paid on ordinary shares (in dollars per share)	$ 0.4	$ 0.36	$ 0.76	$ 0.69
Weighted average ordinary shares outstanding - basic (in shares)	246.0	262.4	247.2	263.6
Weighted average ordinary shares outstanding - diluted (in shares)	247.4	262.4	248.8	265.7