Aon (AON) 10-Q 31 Oct 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014
Document and Entity Information	'
Entity Registrant Name	'Aon plc
Entity Central Index Key	'0000315293
Document Type	'10-Q
Document Period End Date	30-Sep-14
Amendment Flag	'false
Current Fiscal Year End Date	'--12-31
Entity Current Reporting Status	'Yes
Entity Filer Category	'Large Accelerated Filer
Entity Common Stock, Shares Outstanding	285,136,690
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q3

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Income (USD $)	3 Months Ended				9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Revenue	'		'		'		'
Commissions, fees and other	$2,873		$2,786		$8,727		$8,585
Fiduciary investment income	7		8		19		21
Total revenue	2,880		2,794		8,746		8,606
Expenses	'		'		'		'
Compensation and benefits	1,707		1,666		5,166		5,103
Other general expenses	756		764		2,249		2,347
Total operating expenses	2,463		2,430		7,415		7,450
Operating income	417		364		1,331		1,156
Interest income	3		3		7		6
Interest expense	-65		-53		-188		-153
Other income	35		39		34		54
Income before income taxes	390		353		1,184		1,063
Income taxes	75		89		220		275
Net income	315		264		964		788
Less: Net income attributable to noncontrolling interests	6		8		26		30
Net income attributable to Aon shareholders	$309		$256		$938		$758
Basic net income per share attributable to Aon shareholders	$1.06		$0.83		$3.15		$2.42
Diluted net income per share attributable to Aon shareholders	$1.04		$0.82		$3.11		$2.39
Cash dividends per share paid on ordinary shares	$0.25		$0.18		$0.68		$0.51
Weighted average ordinary shares outstanding - basic (in shares)	292.3	[1]	309.5	[1]	298.1	[1]	313.2	[1]
Weighted average ordinary shares outstanding - diluted (in shares)	296.1		312.9		301.6		316.7
[1]	Includes 2.9 million and 3.8 million of participating securities for the three months ended September 30, 2014 and 2013, respectively, and 3.1 million and 4.0 million of participating securities for the nine months ended September 30, 2014 and 2013, respectively.

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net income	$315	$264	$964	$788
Less: Net income attributable to noncontrolling interests	6	8	26	30
Net income attributable to Aon shareholders	309	256	938	758
Other comprehensive (loss) income, net of tax:	'	'	'	'
Change in fair value of investments	0	-14	-1	-1
Change in fair value of derivatives	-8	9	13	-12
Foreign currency translation adjustments	-318	155	-228	-77
Post-retirement benefit obligation	26	24	70	65
Total other comprehensive (loss) income	-300	174	-146	-25
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	3	-2	1
Total other comprehensive (loss) income attributable to Aon shareholders	-300	171	-144	-26
Comprehensive income attributable to Aon shareholders	$9	$427	$794	$732

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Financial Position (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
CURRENT ASSETS	'	'
Cash and cash equivalents	$382	$477
Short-term investments	217	523
Receivables, net	2,630	2,896
Fiduciary assets	10,815	11,871
Other current assets	711	563
Total Current Assets	14,755	16,330
Goodwill	9,026	8,997
Intangible assets, net	2,612	2,578
Fixed assets, net	760	791
Investments	143	132
Other non-current assets	1,531	1,423
TOTAL ASSETS	28,827	30,251
CURRENT LIABILITIES	'	'
Fiduciary liabilities	10,815	11,871
Short-term debt and current portion of long-term debt	660	703
Accounts payable and accrued liabilities	1,528	1,931
Other current liabilities	853	906
Total Current Liabilities	13,856	15,411
Long-term debt	4,840	3,686
Pension, other post-retirement and other post-employment liabilities	1,437	1,607
Other non-current liabilities	1,422	1,352
TOTAL LIABILITIES	21,555	22,056
EQUITY	'	'
Ordinary shares - $0.01 nominal value Authorized: 750 shares (issued: 2014 - 285.1; 2013 - 300.7)	3	3
Additional paid-in capital	5,012	4,785
Retained earnings	4,718	5,731
Accumulated other comprehensive loss	-2,518	-2,374
TOTAL AON SHAREHOLDERS' EQUITY	7,215	8,145
Noncontrolling interests	57	50
TOTAL EQUITY	7,272	8,195
TOTAL LIABILITIES AND EQUITY	$28,827	$30,251

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Financial Position (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, except Per Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Common stock, nominal or par value (in dollars per share)	$0.01	$0.01
Common stock, Authorized shares	750	750
Common stock, issued shares	285.1	300.7

Condensed_Consolidated_Stateme4

Condensed Consolidated Statement of Shareholders' Equity (USD $)	Total	Ordinary Shares and Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss, Net of Tax [Member]	Non-controlling Interests [Member]
In Millions, unless otherwise specified
Beginning Balance at Dec. 31, 2013	$8,195	$4,788	$5,731	($2,374)	$50
Beginning Balance (in shares) at Dec. 31, 2013	300.7	300.7	'	'	'
Increase (Decrease) in Shareholders' Equity	'	'	'	'	'
Net income	964	0	938	0	26
Shares issued - employee benefit plans (in shares)	'	0.4	'	'	'
Shares issued - employee benefit plans	28	28	0	0	0
Shares issued - employee compensation (in shares)	'	4.4	'	'	'
Shares issued - employee compensation	-120	-120	0	0	0
Shares purchased (in shares)	'	-20.4	'	'	'
Shares purchased	-1,750	0	-1,750	0	0
Tax benefit - employee benefit plans	72	72	0	0	0
Share-based compensation expense	247	247	0	0	0
Dividends to shareholders	-201	0	-201	0	0
Net change in fair value of investments	-1	0	0	-1	0
Net change in fair value of derivatives	13	0	0	13	0
Net foreign currency translation adjustments	-228	0	0	-226	-2
Net post-retirement benefit obligation	70	0	0	70	0
Sales (purchases) of shares to (from) noncontrolling interests	-1	0	0	0	-1
Dividends paid to non-controlling interests on subsidiary common stock	-18	0	0	0	-18
Ending Balance at Sep. 30, 2014	$7,272	$5,015	$4,718	($2,518)	$57
Ending Balance (in shares) at Sep. 30, 2014	285.1	285.1	'	'	'

Condensed_Consolidated_Stateme5

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
Net income	$964	$788
Adjustments to reconcile net income to cash provided by operating activities:	'	'
Gain from sales of businesses and investments, net	-41	-28
Depreciation of fixed assets	183	177
Amortization of intangible assets	263	296
Share-based compensation expense	247	207
Deferred income taxes	77	100
Change in assets and liabilities:	'	'
Fiduciary receivables	988	684
Short term investments - funds held on behalf of clients	-177	-369
Fiduciary liabilities	-811	-315
Receivables, net	220	374
Accounts payable and accrued liabilities	-408	-330
Restructuring reserves	-75	-7
Current income taxes	-211	-197
Pension, other post-retirement and other post-employment liabilities	-299	-401
Other assets and liabilities	-37	5
CASH PROVIDED BY OPERATING ACTIVITIES	883	984
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Proceeds from sale of long-term investments	51	81
Purchases of long-term investments	-19	-13
Net sales (purchases) of short-term investments - non-fiduciary	301	-13
Acquisition of businesses, net of cash acquired	-464	-26
Proceeds from sale of businesses	48	6
Capital expenditures	-179	-174
CASH USED FOR INVESTING ACTIVITIES	-262	-139
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Share repurchase	-1,750	-1,025
Issuance of shares for employee benefit plans	58	84
Issuance of debt	4,255	4,270
Repayment of debt	-3,073	-3,870
Cash dividends to shareholders	-201	-159
Sales (purchases) of shares to (from) noncontrolling interests	-1	6
Dividends paid to noncontrolling interests	18	13
Proceeds from sale-leaseback	25	0
CASH USED FOR FINANCING ACTIVITIES	-703	-719
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	-13	-48
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	-95	78
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	477	291
CASH AND CASH EQUIVALENTS AT END OF PERIOD	382	369
Supplemental disclosures:	'	'
Interest paid	194	186
Income taxes paid, net of refunds	$280	$330

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited Condensed Consolidated Financial Statements and Notes thereto have been prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP").  The Condensed Consolidated Financial Statements include the accounts of Aon plc and all controlled subsidiaries ("Aon" or the "Company").  Intercompany accounts and transactions have been eliminated.  The Condensed Consolidated Financial Statements include, in the opinion of management, all adjustments (consisting of normal recurring adjustments and reclassifications) necessary to present fairly the Company's consolidated financial position, results of operations and cash flows for all periods presented.
	Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted.  These Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2013.  The results for the three and nine months ended September 30, 2014 are not necessarily indicative of operating results that may be expected for the full year ending December 31, 2014.
	Use of Estimates
	The preparation of the accompanying unaudited Condensed Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of reserves and expenses. These estimates and assumptions are based on management's best estimates and judgments.  Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, which management believes to be reasonable under the circumstances.  Aon adjusts such estimates and assumptions when facts and circumstances dictate.  Illiquid credit markets, volatile equity markets, and foreign currency movements increase the uncertainty inherent in such estimates and assumptions.  As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates.  Changes in estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods.

Accounting_Principles_and_Prac

Accounting Principles and Practices	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Accounting Principles and Practices	'
	Accounting Principles and Practices
	Changes in Accounting Principles
	Revenue Recognition
	In May 2014, the Financial Accounting Standards Board ("FASB") issued new accounting guidance on revenue from contracts with customers, which will supersede nearly all existing revenue recognition guidance under U.S. GAAP.  The core principal of the guidance is that an entity should recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.  The guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The guidance is effective for Aon in the first quarter of 2017 and early adoption is not permitted. The guidance permits two methods of transition upon adoption; full retrospective and modified retrospective. Under the full retrospective method, prior periods would be restated under the new revenue standard, providing a comparable view across all periods presented. Under the modified retrospective method, prior periods would not be restated. Rather, revenues and other disclosures for pre-2017 periods would be provided in the notes to the financial statements as previously reported under the current revenue standard. The impact from the adoption of this guidance on the Company's Condensed Consolidated Financial Statements cannot be determined at this time. The Company is also working to determine the appropriate method of transition to the guidance.
	Discontinued Operations
	In April 2014, the FASB issued new accounting guidance that increased the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. The guidance is effective for Aon in the first quarter of 2015. The adoption of this guidance is not expected to have a material impact on the Company's Condensed Consolidated Financial Statements.
	Presentation of Unrecognized Tax Benefits
	In July 2013, the FASB issued guidance on the presentation of certain unrecognized tax benefits on financial statements. The guidance requires, unless certain conditions exist, an unrecognized tax benefit to be presented as a reduction to a deferred tax asset in the financial statements for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. The guidance was effective for Aon in the first quarter of 2014. The adoption of this guidance did not have a material impact on the Company's Condensed Consolidated Financial Statements.
	Foreign Currency
	In March 2013, the FASB issued new accounting guidance clarifying the accounting for the release of cumulative translation adjustment into net income when a parent either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. The guidance was effective for Aon in the first quarter of 2014. The adoption of this guidance did not have a material impact on the Company's Condensed Consolidated Financial Statements.

Cash_and_Cash_Equivalents_and_

Cash and Cash Equivalents and Short-term Investments	9 Months Ended
	Sep. 30, 2014
Cash, Cash Equivalents, and Short-term Investments [Abstract]	'
Cash and Cash Equivalents and Short-term Investments	'
	Cash and Cash Equivalents and Short-term Investments
	Cash and cash equivalents include cash balances and all highly liquid investments with initial maturities of three months or less.  Short-term investments include certificates of deposit, money market funds and highly liquid debt instruments purchased with initial maturities in excess of three months but less than one year and are carried at amortized cost, which approximates fair value.
	At September 30, 2014, Cash and cash equivalents and Short-term investments were $599 million compared to $1.0 billion at December 31, 2013. Of the total balance, $144 million and $214 million was restricted as to its use at September 30, 2014 and December 31, 2013, respectively. Included within that amount, at September 30, 2014, the Company is required to hold £40.5 million of operating funds in the U.K. by the Financial Conduct Authority, a U.K.-based regulator, which were included in Short-term investments.  At December 31, 2013, the Company was required to hold £77 million of operating funds in Short-term investments. These operating funds, when translated to U.S. dollars, were equal to $66 million and $126 million at September 30, 2014 and December 31, 2013, respectively. In addition, Cash and cash equivalents included additional restricted balances of $78 million and $88 million at September 30, 2014 and December 31, 2013, respectively. The restricted balances primarily relate to cash required to be held as collateral.

Other_Financial_Data

Other Financial Data	9 Months Ended
	Sep. 30, 2014
Other Financial Data [Abstract]	'
Other Financial Data	'
	Other Financial Data
	Condensed Consolidated Statements of Income Information
	Other Income
	Other income consists of the following (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Equity earnings	$	4		$	6		$	10		$	12
	Gain on investments	4			37			2			36
	Foreign currency remeasurement gain (loss)	7			(4		)	11			15
	Derivative (loss) gain	(6		)	1			(19		)	(8		)
	Gain on disposal of business	25			—			25			—
	Other	1			(1		)	5			(1		)
		$	35		$	39		$	34		$	54
	Condensed Consolidated Statements of Financial Position Information
	Allowance for Doubtful Accounts
	An analysis of the allowance for doubtful accounts is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Balance at beginning of period	$	88		$	114		$	90		$	118
	Provision charged to operations	1			(5		)	9			6
	Accounts written off, net of recoveries	(14		)	(8		)	(23		)	(26		)
	Effect of exchange rate changes and other	4			(2		)	3			1
	Balance at end of period	$	79		$	99		$	79		$	99
	Other Current Assets
	The components of Other current assets are as follows (in millions):
		September 30, 2014			December 31, 2013
	Taxes receivable	258			111
	Prepaid expenses	238			229
	Deferred project costs	102			98
	Deferred tax assets	81			93
	Other	32			32
		$	711		$	563
	Other Non-Current Assets
	The components of Other non-current assets are as follows (in millions):
		September 30, 2014			December 31, 2013
	Prepaid pension (1)	$	750		$	567
	Deferred project costs	256			273
	Deferred tax assets	176			193
	Taxes receivable	98			108
	Other	251			282
		$	1,531		$	1,423
	______________________________________________
	-1	Increase in prepaid pensions is primarily due to cash funding of the U.K. pension plans.
	Other Current Liabilities
	The components of Other current liabilities are as follows (in millions):
		September 30, 2014			December 31, 2013
	Deferred revenue	$	440		$	475
	Taxes payable	96			136
	Deferred tax liabilities	36			48
	Other	281			247
		$	853		$	906
	Other Non-Current Liabilities
	The components of Other non-current liabilities are as follows (in millions):
		September 30, 2014			December 31, 2013
	Deferred tax liabilities	$	535		$	420
	Taxes payable	202			184
	Leases	191			204
	Deferred revenue	170			134
	Compensation and benefits	56			105
	Other	268			305
		$	1,422		$	1,352

Acquisitions_and_Dispositions

Acquisitions and Dispositions	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]	'
Acquisitions and Dispositions	'
	Acquisitions and Dispositions
	Acquisitions
	During the three months ended September 30, 2014, the Company completed the acquisition of four businesses in the Risk Solutions segment and one business in the HR Solutions segment. During the nine months ended September 30, 2014, the Company completed the acquisition of seven businesses in the Risk Solutions segment and two businesses in the HR Solutions segment. During the three months ended September 30, 2013, the Company completed the acquisition of one business in the Risk Solutions segment and one business in the HR Solutions segment. During the nine months ended September 30, 2013, the Company completed the acquisition of five businesses in the Risk Solutions segment and two businesses in the HR Solutions segment.
	The following table includes the aggregate consideration transferred and the preliminary value of intangible assets recorded as a result of the Company's acquisitions (in millions):
		Nine months ended September 30,
		2014		2013
	Consideration	$	446	$	26
	Intangible assets:
	Goodwill	$	261	$	26
	Other intangible assets	310		8
	Total	$	571	$	34
	The results of operations of these acquisitions are included in the Condensed Consolidated Financial Statements as of the acquisition date.  The results of operations of the Company would not have been materially different if these acquisitions had been reported from the beginning of the period in which they were acquired.
	Dispositions
	During the three months ended September 30, 2014, the Company completed the disposition of one business in the Risk Solutions segment. During the nine months ended September 30, 2014, the Company completed the disposition of two businesses in the Risk Solutions segment. A pretax gain of $25 million was recognized on these sales in the both the three and nine months ended September 30, 2014, which is included in Other income in the Condensed Consolidated Statements of Income. During the three months ended September 30, 2013, the Company completed the disposition of one business in the Risk Solutions segment. During the nine months ended September 30, 2013, the Company completed the disposition of five businesses in the Risk Solutions segment.  A pretax gain of $0.2 million gain was recognized on these dispositions in both the three and nine months ended September 30, 2013, which is included in Other income in the Condensed Statements of Income.

Goodwill_and_Other_Intangible_

Goodwill and Other Intangible Assets	9 Months Ended
	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Other Intangible Assets	'
	Goodwill and Other Intangible Assets
	The changes in the net carrying amount of goodwill by reportable segment for the nine months ended September 30, 2014 are as follows (in millions):
		Risk			HR			Total
		Solutions			Solutions
	Balance as of December 31, 2013	$	6,020		$	2,977		$	8,997
	Goodwill related to current year acquisitions	256			5			261
	Goodwill related to disposals	(14		)	—			(14		)
	Goodwill related to prior year acquisitions	(1		)	—			(1		)
	Transfer	(2		)	2			—
	Foreign currency translation	(202		)	(15		)	(217		)
	Balance as of September 30, 2014	$	6,057		$	2,969		$	9,026
	Other intangible assets by asset class are as follows (in millions):
		September 30, 2014									December 31, 2013
		Gross Carrying Amount			Accumulated			Net Carrying Amount			Gross Carrying Amount		Accumulated		Net Carrying Amount
					Amortization								Amortization
	Intangible assets with indefinite lives:
	Tradenames	$	1,019		$	—		$	1,019		$	1,019	$	—	$	1,019
	Intangible assets with finite lives:
	Customer related and contract based	2,972			1,520			1,452			2,720		1,310		1,410
	Marketing, technology and other	588			447			141			584		435		149
		$	4,579		$	1,967		$	2,612		$	4,323	$	1,745	$	2,578
	Amortization expense from finite lived intangible assets was $90 million and $263 million for the three and nine months ended September 30, 2014, respectively. Amortization expense from finite lived intangibles assets was $98 million and $296 million for the three and nine months ended September 30, 2013, respectively.
	The estimated future amortization for finite lived intangible assets as of September 30, 2014 is as follows (in millions):
		Risk Solutions			HR Solutions			Total
	Remainder of 2014	$	29		$	60		$	89
	2015	109			211			320
	2016	100			176			276
	2017	91			140			231
	2018	79			93			172
	Thereafter	253			252			505
		$	661		$	932		$	1,593

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2014
Restructuring and Related Activities [Abstract]	'
Restructuring	'
	Restructuring
	Aon Hewitt Restructuring Plan
	On October 14, 2010, the Company announced a global restructuring plan ("Aon Hewitt Plan") in connection with the acquisition of Hewitt Associates, Inc. The Aon Hewitt Plan was intended to streamline operations across the combined Aon Hewitt organization. The Company incurred all remaining costs for the Aon Hewitt Plan and the plan was closed in the fourth quarter of 2013. For the three and nine months ended September 30, 2014, no charges were taken under the Aon Hewitt Plan. For the three months ended September 30, 2013, $30 million of restructuring expenses were charged, of which $24 million and $6 million were in the Risk Solutions segment and HR Solutions segment, respectively. For the nine months ended September 30, 2013, $109 million of restructuring expenses were charged, of which $52 million and $57 million were in the Risk Solutions segment and HR Solutions segment, respectively.
	As of December 31, 2013, the remaining liabilities for the Company's restructuring plans were $166 million. During the nine months ended September 30, 2014, the Company made cash payments of $70 million, resulting in remaining restructuring liabilities of $90 million as of September 30, 2014. The remaining $6 million reduction in the liability is due fluctuation in foreign exchange rates.

Investments

Investments	9 Months Ended
	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investments	'
	Investments
	The Company earns income on cash balances and investments, as well as on premium trust balances that the Company maintains for premiums collected from insureds but not yet remitted to insurance companies, and funds held under the terms of certain outsourcing agreements to pay certain obligations on behalf of clients.  Premium trust balances and receivables, as well as a corresponding liability, are included in Fiduciary assets and Fiduciary liabilities in the accompanying Condensed Consolidated Statements of Financial Position.
	The Company's interest-bearing assets and other investments are included in the following categories in the Condensed Consolidated Statements of Financial Position (in millions):
		September 30,		December 31,
		2014		2013
	Cash and cash equivalents	$	382	$	477
	Short-term investments	217		523
	Fiduciary assets (1)	3,877		3,778
	Investments	143		132
		$	4,619	$	4,910
	______________________________________________
	-1	Fiduciary assets include funds held on behalf of clients but does not include fiduciary receivables.
	The Company's investments are as follows (in millions):
		September 30,		December 31,
		2014		2013
	Equity method investments	$	122	$	113
	Other investments	13		10
	Fixed-maturity securities	8		9
		$	143	$	132

Debt

Debt	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Debt	'
	Debt
	The Company uses proceeds from the commercial paper market from time to time in order to meet short-term working capital needs and to retire other debt obligations.  At September 30, 2014, the Company had $50 million in commercial paper outstanding compared to no commercial paper outstanding at December 31, 2013. The weighted average commercial paper outstanding for the three and nine months ended September 30, 2014 was $360 million and $338 million, respectively. The weighted average interest rate of the commercial paper outstanding for the three and nine months ended September 30, 2014 was 0.31% and 0.34%, respectively.
	During the quarter ended September 30, 2014, Aon plc's $600 million 3.50% Notes due September 2015 were classified as Short-term debt and current portion of long-term debt in the Condensed Consolidated Statements of Financial Position as the date of maturity is less than one year.
	On August 12, 2014, Aon plc issued $350 million of 3.50% Notes due June 2024. The 3.50% Notes due 2024 constitute a further issuance of, and were consolidated to form a single series of debt securities with, the $250 million of 3.50% Notes due June 2024 issued by the Company on May 20, 2014. The 3.50% Notes due June 2024 are unconditionally guaranteed as to the payment of principal and interest by Aon Corporation. The Company used the proceeds of the issuance for general corporate purposes.
	On June 30, 2014, Aon plc transferred €531 million to a trustee pursuant to an agreement related to the repayment of the €500 million of 6.25% Notes due July 2014 and accrued interest. The trustee subsequently disbursed €531 million to the noteholders on July 1, 2014 in payment of principal and accrued interest. The Company remained the primary obligor of the €500 million of 6.25% Notes due July 2014 until the funds were disbursed from the trustee to the bondholders on July 1, 2014. Therefore, the Company extinguished the liability related to this obligation as of July 1, 2014.
	On May 20, 2014, Aon plc issued $250 million of 3.50% Notes due June 2024 and $550 million of 4.60% Notes due June 2044. The 3.50% Notes due June 2024 and 4.60% Notes due June 2044 are unconditionally guaranteed by Aon Corporation. The Company used the proceeds of the issuance to repay commercial paper borrowings and for general corporate purposes.
	On May 7, 2014, Aon plc issued €500 million of 2.875% Notes due May 2026. The 2.875% Notes due May 2026 are fully and unconditionally guaranteed by Aon Corporation. The Company used the proceeds of the issuance for general corporate purposes, including the repayment at maturity of the Company's then outstanding €500 million of 6.25% Notes due July 2014.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The effective tax rate on net income was 19.1% and 18.5% for the three and nine months ended September 30, 2014, respectively. The effective tax rate on net income was 25.1% and 25.9% for the three and nine months ended September 30, 2013, respectively. The effective tax rate in the third quarter and first nine months of 2014 was favorably impacted by a change in the geographical distribution of income, partially offset by the impact of certain discrete items.

Shareholders_Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Shareholders' Equity	'
	Shareholders' Equity
	Ordinary Shares
	In April 2012, the Company's Board of Directors authorized a share repurchase program under which up to $5.0 billion of Class A Ordinary Shares may be repurchased ("2012 Share Repurchase Program"). Under this program, shares may be repurchased through the open market or in privately negotiated transactions, from time to time, based on prevailing market conditions, and will be funded from available capital.
	In the three months ended September 30, 2014, the Company repurchased 5.8 million shares at an average price per share of $86.07 for a total cost of $500 million under the 2012 Share Repurchase Program. During the nine months ended September 30, 2014, the Company repurchased 20.4 million shares at an average price per share of $85.73 for a total cost of $1.8 billion under the 2012 Share Repurchase Program. In the third quarter of 2013, the Company repurchased 7.3 million shares at an average price per share of $68.33 for a total cost of $500 million under the 2012 Share Repurchase Program. During the nine months ended September 30, 2013, the Company repurchased 15.8 million shares at an average price per share of $64.79 for a total cost of $1.0 billion under the 2012 Share Repurchase Program. The remaining authorized amount for share repurchase under the 2012 Share Repurchase Program is $1.1 billion. Since the inception of the 2012 Share Repurchase Program, the Company repurchased a total of 56.7 million shares for an aggregate cost of $3.9 billion.
	Participating Securities
	Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents, whether paid or unpaid, are participating securities, as defined, and therefore, should be included in computing basic and diluted earnings per share using the two class method.  Certain of the Company's restricted share awards allow the holder to receive a non-forfeitable dividend equivalent.
	Net income attributable to participating securities was $2 million and $7 million in the three and nine months ended September 30, 2014, respectively. Net income attributable to participating securities was $3 million and $8 million in the three and nine months ended September 30, 2013, respectively.
	Weighted average shares outstanding are as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014		2013
	Shares for basic earnings per share (1)	292.3			309.5			298.1		313.2
	Common stock equivalents	3.8			3.4			3.5		3.5
	Shares for diluted earnings per share	296.1			312.9			301.6		316.7
	______________________________________________
	(1) Includes 2.9 million and 3.8 million of participating securities for the three months ended September 30, 2014 and 2013, respectively, and 3.1 million and 4.0 million of participating securities for the nine months ended September 30, 2014 and 2013, respectively.
	Certain ordinary share equivalents may not be included in the computation of diluted net income per share because their inclusion would have been antidilutive. There were no shares excluded from the calculation for the three and nine months ended September 30, 2014 and September 30, 2013.
	Accumulated Other Comprehensive Loss
	Changes in Accumulated other comprehensive loss by component, net of related tax, are as follows (in millions):
		Change in Fair Value of Investments (1)				Change in Fair Value of Derivatives (1)			Foreign Currency Translation Adjustments			Post-Retirement Benefit Obligation (2)			Total
	Balance at December 31, 2013	$	1			$	(22	)	$	169		$	(2,522	)	$	(2,374	)
	Other comprehensive (loss) income before reclassifications, net	(1		)		1			(226		)	2			(224		)
	Amounts reclassified from accumulated other comprehensive loss:
	Amounts reclassified from accumulated other comprehensive loss	—				17			—			94			111
	Tax benefit	—				(5		)	—			(26		)	(31		)
	Amounts reclassified from accumulated other comprehensive loss, net	—				12			—			68			80
	Net current period other comprehensive (loss) income	(1		)		13			(226		)	70			(144		)
	Balance at September 30, 2014	$	—			$	(9	)	$	(57	)	$	(2,452	)	$	(2,518	)
	______________________________________________
	(1) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Other income.
	(2) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Compensation and benefits.

Employee_Benefits

Employee Benefits	9 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Employee Benefits	'
	Employee Benefits
	The following table provides the components of the net periodic benefit cost for Aon's material U.K., U.S., and other significant international pension plans, which are located in the Netherlands and Canada (in millions):
		Three months ended September 30,
		U.K.						U.S.						Other
		2014			2013			2014			2013			2014			2013
	Service cost	$	—		$	—		$	—		$	—		$	—		$	5
	Interest cost	58			52			32			28			12			11
	Expected return on plan assets	(82		)	(74		)	(39		)	(34		)	(15		)	(15		)
	Amortization of net actuarial loss	13			12			11			13			2			6
	Total net periodic (benefit) cost	$	(11	)	$	(10	)	$	4		$	7		$	(1	)	$	7
		Nine months ended September 30,
		U.K.						U.S.						Other
		2014			2013			2014			2013			2014			2013
	Service cost	$	—		$	—		$	—		$	—		$	—		$	14
	Interest cost	174			156			96			84			36			33
	Expected return on plan assets	(247		)	(223		)	(117		)	(103		)	(45		)	(44		)
	Amortization of net actuarial loss	40			36			32			39			6			19
	Net periodic (benefit) cost	(33		)	(31		)	11			20			(3		)	22
	Curtailment loss (gain) and other	—			—			1			—			(3		)	—
	Total net periodic (benefit) cost	$	(33	)	$	(31	)	$	12		$	20		$	(6	)	$	22
	Based on current assumptions, in 2014, Aon plans to contribute $183 million, $173 million, and $29 million to its U.K., U.S. and other significant international pension plans, respectively. During the three months ended September 30, 2014, contributions of $24 million, $39 million, and $7 million were made to the Company's U.K., U.S. and other significant international pension plans, respectively. During the nine months ended September 30, 2014, contributions of $145 million, $112 million, and $23 million were made to the Company's U.K., U.S. and other significant international pension plans, respectively.
	During the three months ended September 30, 2013, contributions of $54 million, $54 million, and $5 million were made to the Company's U.K., U.S. and other significant international pension plans, respectively. During the nine months ended September 30, 2013, contributions of $241 million, $122 million, and $49 million were made to the Company's U.K., U.S. and other significant international pension plans, respectively.

ShareBased_Compensation_Plans

Share-Based Compensation Plans	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-Based Compensation Plans	'
	Share-Based Compensation Plans
	The following table summarizes share-based compensation expense recognized in the Condensed Consolidated Statements of Income in Compensation and benefits (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014				2013
	Restricted share units ("RSUs")	$	41		$	40		$	144			$	135
	Performance share awards ("PSAs")	29			28			96				66
	Share options	—			—			—				1
	Employee share purchase plans	2			2			7				5
	Total share-based compensation expense	$	72		$	70		$	247			$	207
	Restricted Share Units
	A summary of the status of the Company's RSUs is as follows (shares in thousands):
		Nine months ended September 30,
		2014					2013
		Shares		Fair Value (1)			Shares			Fair Value (1)
	Non-vested at beginning of period	9,759		$	51		10,432			$	44
	Granted	2,675		84			3,598			62
	Vested	(3,561	)	49			(3,618	)		44
	Forfeited	(385	)	56			(308	)		47
	Non-vested at end of period	8,488		63			10,104			51
	______________________________________________
	-1	Represents per share weighted average fair value of award at date of grant.
	Performance Share Awards
	The vesting of PSAs is contingent upon meeting a level of earnings per share performance over a three-year period. The performance conditions are not considered in the determination of the grant date fair value for these awards. The fair value of PSAs is based upon the market price of an Aon ordinary share at the date of grant. Compensation expense is recognized over the performance period based on management's estimate of the number of units expected to vest. Compensation expense is adjusted to reflect the actual number of shares issued at the end of the programs. The actual issue of shares may range from 0-200% of the target number of PSAs granted, based on the terms of the plan and level of achievement of the related performance target. Dividend equivalents are not paid on PSAs.
	Information as of September 30, 2014 regarding the Company's target PSAs granted and shares that would be issued at current performance levels for PSAs granted during the nine months ended September 30, 2014 and the years ended December 31, 2013 and 2012, respectively, is as follows (shares in thousands, dollars in millions, except fair value):
		As of September 30, 2014			As of December 31, 2013			As of December 31, 2012
	Target PSAs granted	816			1,135			1,369
	Fair value (1)	$	81		$	58		$	47
	Number of shares that would be issued based on current performance levels	804			2,211			2,656
	Unamortized expense, based on current performance levels	$	52		$	57		$	11
	______________________________________________
	-1	Represents per share weighted average fair value of award at date of grant.
	Share Options
	The Company did not grant any share options during either the nine months ended September 30, 2014 or 2013.
	A summary of the status of the Company's share options and related information is as follows (shares in thousands):
		Nine months ended September 30,
		2014					2013
		Shares		Weighted- Average			Shares			Weighted- Average
				Exercise Price						Exercise Price
	Beginning outstanding	3,462		$	32		5,611			$	32
	Granted	—		—			—			—
	Exercised	(953	)	32			(1,694	)		32
	Forfeited and expired	(6	)	37			(29	)		34
	Outstanding at end of period	2,503		32			3,888			32
	Exercisable at end of period	2,464		32			3,681			32
	The weighted average remaining contractual life, in years, of outstanding options was 1.7 years and 2.2 years at September 30, 2014 and 2013, respectively.
	The aggregate intrinsic value represents the total pretax intrinsic value, based on options with an exercise price less than the Company's closing share price of $87.67 as of September 30, 2014, which would have been received by the option holders had those option holders exercised their options as of that date.  At September 30, 2014, the aggregate intrinsic value of options outstanding was $138 million, of which $137 million was exercisable.
	Other information related to the Company's share options is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014				2013
	Aggregate intrinsic value of stock options exercised	$	6		$	14		$	51			$	53
	Cash received from the exercise of stock options	3			14			30				55
	Tax benefit realized from the exercise of stock options	2			3			14				10
	Unamortized deferred compensation expense, which includes both options and awards, amounted to $395 million as of September 30, 2014, with a remaining weighted-average amortization period of approximately 2.1 years.

Derivatives_and_Hedging

Derivatives and Hedging	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivatives and Hedging	'
	Derivatives and Hedging
	The Company is exposed to market risks, including changes in foreign currency exchange rates and interest rates.  To manage the risk related to these exposures, the Company enters into various derivative instruments that reduce these risks by creating offsetting exposures.  The Company does not enter into derivative transactions for trading or speculative purposes.
	Foreign Exchange Risk Management
	The Company is exposed to foreign exchange risk when it receives revenues, pays expenses, or enters into intercompany loans denominated in a currency that differs from its functional currency, or other transactions that are denominated in a currency other than its functional currency.  The Company uses foreign exchange derivatives, typically forward contracts, options and cross currency swaps, to reduce its overall exposure to the effects of currency fluctuations on cash flows.  These exposures are hedged, on average, for less than two years; however, in limited instances, the Company has hedged certain exposures up to five years in the future.
	The Company also uses foreign exchange derivatives, typically forward contracts and options, to hedge its net investments in foreign operations for up to two years in the future, and to manage the currency exposure of the Company's global liquidity profile, including monetary assets or liabilities that are denominated in a non-functional currency of an entity, for up to one year in the future. These derivatives are not accounted for as hedges, and changes in fair value are recorded each period in Other income in the Condensed Consolidated Statements of Income.
	Interest Rate Risk Management
	The Company holds variable-rate short-term brokerage and other operating deposits. The Company uses interest rate derivatives, typically swaps, to reduce its exposure to the effects of interest rate fluctuations on the forecasted interest receipts from these deposits for up to two years in the future.
	Certain derivatives also give rise to credit risks from the possible non-performance by counterparties.  The credit risk at the balance sheet date is generally limited to the fair value of those contracts that are favorable to the Company.  The Company has reduced its credit risk by (1) using International Swaps and Derivatives Association master agreements, collateral and credit support arrangements, (2) entering into non-exchange-traded derivatives with highly-rated major financial institutions and (3) using exchange-traded instruments.  The Company monitors the creditworthiness of, and exposure to, its counterparties.  As of September 30, 2014, all net derivative positions were free of credit risk contingent features.  The Company has not received or pledged any collateral related to derivative arrangements as of September 30, 2014.
	The notional and fair values of derivative instruments are as follows (in millions):
		Notional Amount						Derivative Assets (1)						Derivative Liabilities (2)
		September 30,			December 31,			September 30,			December 31,			September 30,			December 31,
		2014			2013			2014			2013			2014			2013
	Derivatives accounted for as hedges:
	Interest rate contracts	$	—		$	171		$	—		$	9		$	—		$	—
	Foreign exchange contracts	1,106			1,191			55			71			65			93
	Total	1,106			1,362			55			80			65			93
	Derivatives not accounted for as hedges:
	Foreign exchange contracts	184			215			—			—			—			—
	Total	$	1,290		$	1,577		$	55		$	80		$	65		$	93
	______________________________________________
	-1	Included within Other current assets ($25 million and $46 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current assets ($30 million and $34 million at September 30, 2014 and December 31, 2013, respectively).
	-2	Included within Other current liabilities ($17 million and $51 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current liabilities ($48 million and $42 million at September 30, 2014 and December 31, 2013, respectively).
	Offsetting of financial assets and derivatives assets are as follows (in millions):
		Gross Amounts of Recognized Assets						Gross Amounts Offset in the Statement of Financial Position						Net Amounts of Assets Presented in the Statement of Financial Position (1)
		September 30,			December 31,			September 30,			December 31,			September 30,			December 31,
		2014			2013			2014			2013			2014			2013
	Derivatives accounted for as hedges:
	Interest rate contracts	$	—		$	9		$	—		$	—		$	—		$	9
	Foreign exchange contracts	55			71			(15		)	(30		)	40			41
	Total	55			80			(15		)	(30		)	40			50
	Derivatives not accounted for as hedges:
	Foreign exchange contracts	—			—			—			—			—			—
	Total	$	55		$	80		$	(15	)	$	(30	)	$	40		$	50
	______________________________________________
	(1) Included within Other current assets ($13 million and $18 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current assets ($27 million and $32 million at September 30, 2014 and December 31, 2013, respectively).
	Offsetting of financial liabilities and derivative liabilities are as follows (in millions):
		Gross Amounts of Recognized Liabilities						Gross Amounts Offset in the Statement of Financial Position						Net Amounts of Liabilities Presented in the Statement of Financial Position (1)
		September 30,			December 31,			September 30,			December 31,			September 30,			December 31,
		2014			2013			2014			2013			2014			2013
	Derivatives accounted for as hedges:
	Interest rate contracts	$	—		$	—		$	—		$	—		$	—		$	—
	Foreign exchange contracts	65			93			(15		)	(30		)	50			63
	Total	65			93			(15		)	(30		)	50			63
	Derivatives not accounted for as hedges:
	Foreign exchange contracts	—			—			—			—			—			—
	Total	$	65		$	93		$	(15	)	$	(30	)	$	50		$	63
	______________________________________________
	(1) Included within Other current liabilities ($5 million and $23 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current liabilities ($45 million and $40 million at September 30, 2014 and December 31, 2013, respectively).
	The amounts of derivative gains (losses) recognized in the Condensed Consolidated Financial Statements for the three and nine months ended September 30, 2014 and 2013 are as follows (in millions):
	Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Cash flow hedges:
	Interest rate contracts (1)	$	—		$	—		$	—		$	—
	Foreign exchange contracts (2)	(3		)	—			4			(28		)
	Total	$	(3	)	$	—		$	4		$	(28	)
	______________________________________________
	(1) Location of future reclassification from Accumulated Other Comprehensive Loss will be included within Interest expense.
	(2) Location of future reclassification from Accumulated Other Comprehensive Loss will be included within Compensation and benefits ($2 million and $3 million loss for the three months ended September 30, 2014 and 2013, respectively, and $14 million gain and $17 million loss for the nine months ended September 30, 2014 and 2013, respectively), Other income ($2 million and $3 million gain for the three months ended September 30, 2014 and 2013, respectively, and $9 million and $11 million loss for the nine months ended September 30, 2014 and 2013, respectively), and Other general expenses ($3 million and $1 million loss for the three and nine months ended September 30, 2014, respectively).
	Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Cash flow hedges:
	Interest rate contracts (1)	$	—		$	—		$	(1	)	$	(1	)
	Foreign exchange contracts (2)	4			(10		)	(15		)	(7		)
Total	4			(10		)	(16		)	(8		)
______________________________________________
(1) Included within Interest expense
(2) Included within Compensation and benefits ($1 million and $5 million loss for the three months ended September 30, 2014 and 2013, respectively, and $4 million and $9 million loss for the nine months ended September 30, 2014 and 2013, respectively), Other income ($5 million gain and $5 million loss for the three months ended September 30, 2014 and 2013, respectively, and $6 million loss and $3 million gain for the nine months ended September 30, 2014 and 2013, respectively), Interest expenses ($3 million and $8 million loss for the three and nine months ended September 30, 2014, respectively), and Other general expenses ($3 million gain for the three months ended September 30, 2014, and $3 million gain and $1 million loss for the nine months ended September 30, 2014 and 2013, respectively).
The amount of gain (loss) recognized in the Condensed Consolidated Financial Statements is as follows (in millions):
	Three months ended September 30,												Nine months ended September 30,
	Amount of Gain (Loss) Recognized in Income on Derivative (1)						Amount of Gain (Loss) Recognized in Income on Related Hedged Item						Amount of Gain (Loss) Recognized in Income on Derivative (1) (2)						Amount of Gain (Loss) Recognized in Income on Related Hedge Item (1) (2)
	2014			2013			2014			2013			2014			2013			2014		2013
Fair value hedges:
Foreign exchange contracts (2)	$	(9	)	$	(7	)	$	9		$	7		$	(9	)	$	(8	)	$	9	$	8
______________________________________________
(1) Included in Interest expense.
(2) Relates to fixed rate debt.
The Company estimates that approximately $3 million of pretax losses currently included within Accumulated other comprehensive loss will be reclassified into earnings in the next twelve months.
The amount of gain (loss) recognized in income on the ineffective portion of derivatives for the three and nine months ended September 30, 2014 and 2013 was not material.
During the three and nine months ended September 30, 2014, the Company recorded a loss of $11 million and $13 million, respectively, in Other income, for foreign exchange derivatives not designated or qualifying as hedges. During the three and nine months ended September 30, 2013, the Company recorded a gain of $3 million and a loss of $15 million, respectively, in Other income, for foreign exchange derivatives not designated or qualifying as hedges.

Fair_Value_Measurements_and_Fi

Fair Value Measurements and Financial Instruments	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements and Financial Instruments	'
	Fair Value Measurements and Financial Instruments
	Accounting standards establish a three tier fair value hierarchy that prioritizes the inputs used in measuring fair values as follows:
	•	Level 1 — observable inputs such as quoted prices for identical assets in active markets;
	•	Level 2 — inputs other than quoted prices for identical assets in active markets, that are observable either directly or indirectly; and
	•	Level 3 — unobservable inputs in which there is little or no market data which requires the use of valuation techniques and the development of assumptions.
	The following methods and assumptions are used to estimate the fair values of the Company's financial instruments:
	Money market funds and highly liquid debt securities are carried at cost and amortized cost, respectively, as an approximation of fair value. Based on market convention, the Company considers cost a practical and expedient measure of fair value.
	Cash, cash equivalents, and highly liquid debt instruments consist of cash and institutional short-term investment funds. The Company independently reviews the short-term investment funds to obtain reasonable assurance the fund net asset value is $1 per share.
	Equity investments consist of domestic and international equity securities and exchange traded equity derivatives valued using the closing stock price on a national securities exchange. Over the counter equity derivatives are valued using observable inputs such as underlying prices of the equity security and volatility. The Company independently reviews the listing of Level 1 equity securities in the portfolio and agrees the closing stock prices to a national securities exchange, and on a sample basis, independently verifies the observable inputs for Level 2 equity derivatives and securities.
	Fixed income investments consist of certain categories of bonds and derivatives. Corporate, government, and agency bonds are valued by pricing vendors who estimate fair value using recently executed transactions and proprietary models based on observable inputs, such as interest rate spreads, yield curves and credit risk. Asset-backed securities are valued by pricing vendors who estimate fair value using discounted cash flow models utilizing observable inputs based on trade and quote activity of securities with similar features. Fixed income derivatives are valued by pricing vendors using observable inputs such as interest rates and yield curves. The Company obtains a detailed understanding of the models, inputs, and assumptions used in developing prices provided by its vendors. This understanding includes discussions with valuation resources at the vendor. During these discussions, the Company uses a fair value measurement questionnaire, which is part of the Company's internal controls over financial reporting, to obtain the information necessary to assert the model, inputs and assumptions used comply with U.S. GAAP, including disclosure requirements. The Company also obtains observable inputs from the pricing vendor and independently verifies the observable inputs, as well as assesses assumptions used for reasonableness based on relevant market conditions and internal Company guidelines. If an assumption is deemed unreasonable, based on the Company's guidelines, it is then reviewed by a member of management and the fair value estimate provided by the vendor is adjusted, if deemed appropriate. These adjustments do not occur frequently and have not historically been material to the fair value estimates used in the Condensed Consolidated Financial Statements.
	Pooled funds consist of various equity, fixed income, commodity, and real estate mutual fund type investment vehicles. Pooled investment funds fair value is estimated based on the proportionate share ownership in the underlying net assets of the investment, which is based on the fair value of the underlying securities that trade on a national securities exchange. Where possible, the Company independently reviews the listing of securities in the portfolio and agrees the closing stock prices to the price quoted on a national securities exchange. The Company gains an understanding of the investment guidelines and valuation policies of the fund and discusses fund performance with pooled fund managers. The Company obtains audited fund manager financial statements, when available. If the pooled fund is designed to replicate a publicly traded index, the Company compares the performance of the fund to the index to assess the reasonableness of the fair value measurement.
	Alternative investments consist of limited partnerships, private equity and hedge funds. Alternative investment fair value is generally estimated based on the proportionate share ownership in the underlying net assets of the investment as determined by the general partner or investment manager. The valuations are based on various factors depending on investment strategy, proprietary models, and specific financial data or projections. The Company obtains audited fund manager financial statements, when available. The Company obtains a detailed understanding of the models, inputs and assumptions used in developing prices provided by the investment managers (or appropriate party) through regular discussions. During these discussions with the investment managers, the Company uses a fair value measurement questionnaire, which is part of the Company's internal controls over financial reporting, to obtain the information necessary to assert the model, inputs and assumptions used comply with U.S. GAAP, including disclosure requirements. The Company also obtains observable inputs from the investment manager and independently verifies the observable inputs, as well as assesses assumptions used for reasonableness based on relevant market conditions and internal Company guidelines. If an assumption is deemed unreasonable, based on the Company's guidelines, it is then reviewed by a member of management and the fair value estimate provided by the vendor is adjusted, if deemed appropriate. These adjustments do not occur frequently and have not historically been material to the fair value estimates in the Condensed Consolidated Financial Statements.
	Derivatives are carried at fair value, based upon industry standard valuation techniques that use, where possible, current market-based or independently sourced pricing inputs, such as interest rates, currency exchange rates, or implied volatilities.
	Annuity contracts consist of insurance group annuity contracts purchased to match the pension benefit payment stream owed to certain selected plan participant demographics within a few major U.K. defined benefit plans. Annuity contracts are valued using a discounted cash flow model utilizing assumptions such as discount rate, mortality, and inflation. The Company independently verifies the observable inputs.
	Real estate and REITs consist of publicly traded real estate investment trusts ("REITs") and direct real estate investments. Level 1 REITs are valued using the closing stock price on a national securities exchange. The Level 3 values are based on the proportionate share of ownership in the underlying net asset value as determined by the investment manager. The Company independently reviews the listing of Level 1 REIT securities in the portfolio and agrees the closing stock prices to a national securities exchange. The Company gains an understanding of the investment guidelines and valuation policies of the Level 3 real estate funds and discusses performance with the fund managers. The Company obtains audited fund manager financial statements, when available. See the description of "Alternative investments" for further detail on valuation procedures surrounding Level 3 REITs.
	Guarantees are carried at fair value, which is based on discounted estimated cash flows using published historical cumulative default rates and discount rates commensurate with the underlying exposure.
	Debt is carried at outstanding principal balance, less any unamortized discount or premium. Fair value is based on quoted market prices or estimates using discounted cash flow analyses based on current borrowing rates for similar types of borrowing arrangements.
	The following tables present the categorization of the Company's assets and liabilities that are measured at fair value on a recurring basis at September 30, 2014 and December 31, 2013 (in millions):
				Fair Value Measurements Using
		Balance at September 30, 2014		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	Assets:
	Money market funds and highly liquid debt securities (1)	$	1,649	$	1,647	$	2	$	—
	Other investments:
	Fixed maturity securities:
	Corporate bonds	1		—		—		1
	Government bonds	7		—		7		—
	Equity securities	11		6		5		—
	Derivatives:
	Interest rate contracts	—		—		—		—
	Foreign exchange contracts	55		—		55		—
	Liabilities:
	Derivatives:
	Foreign exchange contracts	65		—		65		—
	______________________________________________
	(1) Includes $1,647 million of money market funds and $2 million of highly liquid debt securities that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity.  See Note 8 "Investments" for additional information regarding the Company's investments.
				Fair Value Measurements Using
		Balance at December 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	Assets:
	Money market funds and highly liquid debt securities (1)	$	2,079	$	2,054	$	25	$	—
	Other investments:
	Fixed maturity securities:
	Corporate bonds	2		—		—		2
	Government bonds	7		—		7		—
	Equity securities	13		6		7		—
	Derivatives:
	Interest rate contracts	9		—		9		—
	Foreign exchange contracts	71		—		71		—
	Liabilities:
	Derivatives:
	Foreign exchange contracts	93		—		93		—
	______________________________________________
	(1)  Includes $2,054 million of money market funds and $25 million of highly liquid debt securities that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity.  See Note 8 "Investments" for additional information regarding the Company's investments.
	There were no transfers of assets or liabilities between fair value hierarchy levels in the three and nine months ended September 30, 2014 and 2013, respectively. There were no realized or unrealized gains or losses recognized in the Condensed Consolidated Statements of Income during the three and nine months ended September 30, 2014, related to assets and liabilities measured at fair value using unobservable inputs. There were $6 million of realized gains and no unrealized gains or losses recognized in the Condensed Consolidated Statements of Income during the three and nine months ended September 30, 2013, related to assets and liabilities measured at fair value using unobservable inputs.
	The fair value of Long-term debt is classified as Level 2 of the fair value hierarchy. The following table discloses the Company's financial instruments where the carrying amounts and fair values differ (in millions):
		September 30, 2014				December 31, 2013
		Carrying Value		Fair Value		Carrying Value		Fair Value
	Long-term debt	$	4,840	$	5,190	$	3,686	$	3,894

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Legal
	Aon and its subsidiaries are subject to numerous claims, tax assessments, lawsuits and proceedings that arise in the ordinary course of business, which frequently include errors and omissions ("E&O") claims. The damages claimed in these matters are or may be substantial, including, in many instances, claims for punitive, treble or extraordinary damages. Aon has historically purchased E&O insurance and other insurance to provide protection against certain losses that arise in such matters. Aon has exhausted or materially depleted its coverage under some of the policies that protect the Company and, consequently, is self-insured or materially self-insured for some claims. Accruals for these exposures, and related insurance receivables, when applicable, are included in the Condensed Consolidated Statements of Financial Position and have been recognized in Other general expenses in the Condensed Consolidated Statements of Income to the extent that losses are deemed probable and are reasonably estimable. These amounts are adjusted from time to time as developments warrant. Matters that are not probable and estimable are not accrued for in the financial statements. Included in the matters described below are matters in which (1) loss is probable (2) loss is reasonably possible but not probable or (3) there exists the reasonable possibility of loss greater than the accrued amount. The reasonably possible range of loss for the matters described below, in excess of amounts that are deemed probable and estimable and therefore already accrued, is estimated to be between $0 and $0.7 billion, exclusive of any insurance coverage. These estimates are based on currently available information. As available information changes, the matters for which Aon is able to estimate will change, and the estimates themselves will change. In addition, many estimates involve significant judgment and uncertainty. For example, at the time of making an estimate, Aon may only have limited information about the facts underlying the claim, and predictions and assumptions about future court rulings and outcomes may prove to be inaccurate.
	Although management at present believes that the ultimate outcome of all matters described below, individually or in the aggregate, will not have a material adverse effect on the consolidated financial position of Aon, legal proceedings are subject to inherent uncertainties and unfavorable rulings or other events. Unfavorable resolutions could include substantial monetary or punitive damages imposed on Aon or its subsidiaries. If unfavorable outcomes of these matters were to occur, future results of operations or cash flows for any particular quarterly or annual period could be materially adversely affected.
	A predecessor of a retail insurance brokerage subsidiary of Aon provided insurance brokerage services to Northrop Grumman Corporation ("Northrop"). This subsidiary placed Northrop's property insurance program for the period covering 2005. Northrop suffered a substantial loss in August 2005 when Hurricane Katrina damaged Northrop's shipbuilding facilities in the Gulf States. Northrop's excess insurance carrier, Factory Mutual Insurance Company ("Factory Mutual"), denied coverage for storm surge damage pursuant to a flood exclusion in the excess policy. Northrop sued Factory Mutual in the United States District Court for the Central District of California. The district court granted summary judgment in Northrop's favor in August 2007. In August 2008, the United State Court of Appeals for the Ninth Circuit reversed the district court's ruling and held that the flood exclusion applied to storm surge damage. Northrop thereafter sought to join Aon's subsidiary as a defendant in the action against Factory Mutual, asserting that if Northrop's policy with Factory Mutual does not cover the Northrop storm surge losses, then the Aon subsidiary will be responsible for Northrop's losses. In August 2010, the court granted in large part Factory Mutual's motion for partial summary judgment regarding the applicability of the flood exclusion and denied Northrop's motion to add the Aon subsidiary as a defendant in the federal lawsuit. On January 27, 2011, Northrop filed suit against the Aon subsidiary in the Superior Court of the State of California, County of Los Angeles, asserting claims for negligence, breach of contract and negligent misrepresentation. Northrop later settled its claims with Factory Mutual. In January 2014, Northrop filed an amended complaint, adding additional claims against the Aon subsidiary for intentional misrepresentation and concealment. Northrop seeks compensatory damages of approximately $340 million, which includes prejudgment interest and attorneys' fees, and punitive damages that are a multiple of the compensatory damages sought. Aon asserts several defenses, including, but not limited to, that it committed no error or omission in placing the Factory Mutual excess policy for Northrop and that Northrop did not suffer any damages as a result of Aon's conduct.
	Another retail insurance brokerage subsidiary of Aon was sued on September 14, 2010 in the Chancery Court for Davidson County, Tennessee Twentieth Judicial District, at Nashville by a client, Opry Mills Mall Limited Partnership ("Opry Mills") that sustained flood damage to its property in May 2010. The lawsuit seeks $200 million from numerous insurers with whom this Aon subsidiary placed the client's property insurance coverage. The insurers contend that only $50 million in coverage is available for the loss because the flood event occurred on property in a high hazard flood zone. Opry Mills is seeking full coverage from the insurers for the loss and has sued this Aon subsidiary in the alternative for the same $150 million difference on various theories of professional liability if the court determines there is not full coverage. In addition, Opry Mills seeks prejudgment interest, attorneys' fees and enhanced damages which could substantially increase Aon's exposure. Aon believes it has meritorious defenses and intends to vigorously defend itself against these claims.
	A pensions consulting and administration subsidiary of Hewitt before its acquisition by Aon provided advisory services to the Trustees of the Philips UK pension fund and the relevant employer of fund beneficiaries. On January 2, 2014, Philips Pension Trustees Limited and Philips Electronics UK Limited (together, "Philips") sued Aon in the High Court, Chancery Division, London alleging negligence and breach of duty. The proceedings assert Philips' right to claim damages related to Philips' use of a credit default swap hedging strategy pursuant to the supply of the advisory services, which is said to have resulted in substantial damages to Philips. Philips is seeking approximately £189 million ($307 million at September 30, 2014 exchange rates), plus interest and costs. Aon believes that it has meritorious defenses and intends to vigorously defend itself against these allegations.
	On December 21, 2012, Mazeikiu Nafta ("MN"), which operates an oil refinery in Lithuania, sued an insurance brokerage subsidiary of Aon in the High Court of Justice in England & Wales, Queen's Bench Division, Commercial Court. Aon placed property damage and business interruption coverage for MN. There was a fire at the refinery in 2006. MN settled with insurers in November 2011. The claim was for $125 million, which was the shortfall alleged by MN to have been caused by Aon's failure to obtain appropriate business interruption coverage. On October 27, 2014, following 11 days of trial, the case was settled for $5 million with no admission of liability on the part of Aon.
	On June 1, 2007, the International Road Transport Union ("IRU") sued Aon in the Geneva Tribunal of First Instance in Switzerland. IRU alleges, among other things, that, between 1995 and 2004, a predecessor of Aon and, later, an Aon subsidiary (1) accepted commissions for certain insurance placements that violated a fee agreement entered between the parties and (2) negligently failed to ask certain insurance carriers to contribute to the IRU's risk management costs.  IRU seeks damages of approximately CHF 46 million ($48 million at September 30, 2014 exchange rates) and $3 million, plus legal fees and interest of approximately $30 million. Aon believes that it has meritorious defenses and intends to vigorously defend itself against these claims.
	On December 27, 2012, AXA Versicherung Aktiengesellschaft ("AXA") started arbitral proceedings in Hamburg, Germany against an insurance and reinsurance brokerage subsidiary of Aon in Germany.  Predecessors of AXA granted predecessors of the Aon subsidiary a mandate to underwrite non-proportional reinsurance business from 1975 through 1999. AXA alleges, among other things, that the Aon-related entities intentionally exceeded their mandate and that, if AXA had known of this intention, it would not have granted a mandate.  AXA seeks damages of approximately €183 million ($232 million at September 30, 2014 exchange rates). Aon believes that it has meritorious defenses and intends to vigorously defend itself against these claims.
	A pensions consulting and administration subsidiary of Aon provided advisory services to the Trustees of the Gleeds pension fund in the United Kingdom and, on occasion, to the relevant employer of the fund.  In April 2014, the High Court, Chancery Division, London found that certain governing documents of the fund that sought to alter the fund's benefit structure and that had been drafted by Aon were procedurally defective and therefore invalid.  No lawsuit naming Aon as a party has been filed, although a tolling agreement has been entered.  The High Court decision says that the additional liabilities in the pension fund resulting from the alleged defect in governing documents amount to approximately £45 million ($73 million at September 30, 2014 exchange rates). Aon believes that it has meritorious defenses and intends to vigorously defend itself against this potential claim.
	From time to time, Aon's clients may bring claims and take legal action pertaining to the performance of fiduciary responsibilities. Whether client claims and legal action related to the Company's performance of fiduciary responsibilities are founded or unfounded, if such claims and legal actions are resolved in a manner unfavorable to the Company, they may adversely affect Aon's financial results and materially impair the market perception of the Company and that of its products and services.
	Guarantees and Indemnifications
	In connection with the redomicile of Aon's headquarters (the "Redomestication"), the Company on April 2, 2012 entered various agreements pursuant to which it agreed to guarantee the obligations of its subsidiaries arising under issued and outstanding debt securities. Those agreements included the (1) Amended and Restated Indenture, dated as of April 2, 2012, among Aon Corporation, Aon plc, and The Bank of New York Mellon Trust Company, N.A., as trustee (the "Trustee") (amending and restating the Indenture, dated as of September 10, 2010, between Aon Corporation and the Trustee), (2) Amended and Restated Indenture, dated as of April 2, 2012, among Aon Corporation, Aon plc and the Trustee (amending and restating the Indenture, dated as of December 16, 2002, between Aon Corporation and the Trustee), (3) Amended and Restated Indenture, dated as of April 2, 2012, among Aon Corporation, Aon plc and the Trustee (amending and restating the Indenture, dated as of January 13, 1997, as supplemented by the First Supplemental Indenture, dated as of January 13, 1997) (4) First Supplemental Indenture, dated as of April 2, 2012, among Aon Finance N.S. 1, ULC, as issuer, Aon Corporation, as guarantor, Aon plc, as guarantor, and Computershare Trust Company of Canada, as trustee, and (5) Amended and Restated Trust Deed, among Aon Corporation, Aon plc, Aon Services Luxembourg & Co S.C.A. (formerly known as Aon Financial Services Luxembourg S.A.) ("Aon Luxembourg") and BNY Mellon Corporate Trustee Services Limited, as trustee (the "Luxembourg Trustee") (amending and restating the Trust Deed, dated as of July 1, 2009, as amended and restated on January 12, 2011, among Aon Delaware, Aon Luxembourg and the Luxembourg Trustee).
	Effective as of the same date, the Company also entered into agreements pursuant to which it agreed to guarantee the obligations of its subsidiaries arising under the (1) $450,000,000 Term Credit Agreement dated June 15, 2011, among Aon Corporation, as borrower, Bank of America, N.A., as administrative agent and the other agents and lenders party thereto, (2) $400,000,000 Five-Year Agreement dated March 20, 2012, among Aon Corporation, as borrower, Citibank, N.A., as administrative agent and the other agents and lenders party thereto and (3) €650,000,000 Facility Agreement, dated October 15, 2010, among Aon Corporation, the subsidiaries of Aon Corporation party thereto as borrowers, Citibank International plc, as agent, and the other agents and lenders party thereto, as amended on July 18, 2011.
	The Company provides a variety of guarantees and indemnifications to its customers and others. The maximum potential amount of future payments represents the notional amounts that could become payable under the guarantees and indemnifications if there were a total default by the guaranteed parties, without consideration of possible recoveries under recourse provisions or other methods. These amounts may bear no relationship to the expected future payments, if any, for these guarantees and indemnifications. Any anticipated amounts payable are included in the Company's Condensed Consolidated Financial Statements, and are recorded at fair value.
	The Company expects that, as prudent business interests dictate, additional guarantees and indemnifications may be issued from time to time.
	Letters of Credit
	The Company had total letters of credit ("LOCs") outstanding for approximately $97 million at September 30, 2014, compared to $71 million at December 31, 2013. These letters of credit cover the beneficiaries related to certain of Aon's U.S. and Canadian non-qualified pension plan schemes and secure deductible retentions for Aon's own workers compensation program. The Company has also issued LOCs to cover contingent payments for taxes and other business obligations to third parties, and other guarantees for miscellaneous purposes at its international subsidiaries. Amounts are accrued in the Condensed Consolidated Financial Statements, and are recorded at fair value.
	Commitments
	The Company has provided commitments to fund certain limited partnerships in which it has an interest in the event that the general partners request funding. Some of these commitments have specific expiration dates and the maximum potential funding under these commitments was $16 million at September 30, 2014 compared to $34 million at December 31, 2013. During the three and nine months ended September 30, 2014, the Company funded $4 million and $18 million of these commitments, respectively.
	Premium Payments
	The Company has certain contractual contingent guarantees for premium payments owed by clients to certain insurance companies. Costs associated with these guarantees, to the extent estimable and probable, are provided in Aon's allowance for doubtful accounts. The maximum exposure with respect to such contractual contingent guarantees was approximately $83 million at September 30, 2014 compared to $98 million at December 31, 2013.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	Segment Information
	The Company has two reportable segments:  Risk Solutions and HR Solutions.  Unallocated income and expenses, when combined with the operating segments and after the elimination of intersegment revenues and expenses, equal the amounts in the Condensed Consolidated Financial Statements.
	Reportable operating segments have been determined using a management approach, which is consistent with the basis and manner in which Aon's chief operating decision-maker ("CODM") uses financial information for the purposes of allocating resources and evaluating performance.  The CODM assesses performance based on operating income and generally accounts for inter-segment revenue as if the revenue were from third parties and at what management believes are current market prices.  The Company does not present net assets by segment as this information is not reviewed by the CODM.
	Risk Solutions acts as an advisor and insurance and reinsurance broker, helping clients manage their risks, via consultation, as well as negotiation and placement of insurance risk with insurance carriers through Aon's global distribution network.
	HR Solutions partners with organizations to solve their most complex benefits, talent and related financial challenges, and improve business performance by designing, implementing, communicating and administering a wide range of human capital, retirement, investment management, health care, compensation and talent management strategies.
	Aon's total revenue is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Risk Solutions	$	1,836		$	1,821		$	5,778		$	5,736
	HR Solutions	1,057			981			3,004			2,891
	Intersegment eliminations	(13		)	(8		)	(36		)	(21		)
	Total revenue	$	2,880		$	2,794		$	8,746		$	8,606
	Commissions, fees and other revenues by product are as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Retail brokerage	$	1,458		$	1,424		$	4,619		$	4,548
	Reinsurance brokerage	371			389			1,140			1,167
	Total Risk Solutions Segment	1,829			1,813			5,759			5,715
	Consulting services	466			406			1,245			1,176
	Outsourcing	604			587			1,788			1,746
	Intrasegment	(13		)	(12		)	(29		)	(31		)
	Total HR Solutions Segment	1,057			981			3,004			2,891
	Intersegment	(13		)	(8		)	(36		)	(21		)
	Total commissions, fees and other revenue	$	2,873		$	2,786		$	8,727		$	8,585
	Fiduciary investment income by segment is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Risk Solutions	$	7		$	8		$	19		$	21
	HR Solutions	—			—			—			—
	Total fiduciary investment income	$	7		$	8		$	19		$	21
	A reconciliation of segment operating income before tax to income before income taxes is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Risk Solutions	$	343		$	333		$	1,205		$	1,127
	HR Solutions	113			75			249			162
	Segment income before income taxes	456			408			1,454			1,289
	Unallocated expenses	(39		)	(44		)	(123		)	(133		)
	Interest income	3			3			7			6
	Interest expense	(65		)	(53		)	(188		)	(153		)
	Other income	35			39			34			54
	Income before income taxes	$	390		$	353		$	1,184		$	1,063
	Unallocated expenses include administrative or other costs not attributable to the operating segments, such as corporate governance costs. Interest income represents income earned primarily on operating cash balances and certain income producing securities. Interest expense represents the cost of debt obligations.
	Other income consists of equity earnings, realized gains or losses on the sale of investments, gains or losses on the disposal of businesses, gains or losses on derivatives, and gains or losses on foreign currency transactions.

Guarantee_of_Registered_Securi

Guarantee of Registered Securities	9 Months Ended
	Sep. 30, 2014
Guarantee of Registered Securities [Abstract]	'
Guarantee of Registered Securities	'
	Guarantee of Registered Securities
	As described in Note 16, in connection with the Redomestication, Aon plc entered into various agreements pursuant to which it agreed to guarantee the obligations of Aon Corporation arising under issued and outstanding debt securities. Aon Corporation is a 100% directly owned subsidiary of Aon plc. The debt securities that are subject to Rule 3-10 of Regulation S-X are the 3.50% Notes due September 2015, the 3.125% Notes due May 2016, the 5.00% Notes due September 2020, the 8.205% Notes due January 2027 and the 6.25% Notes due September 2040. All guarantees of Aon plc are full and unconditional. There are no other subsidiaries of Aon plc that are guarantors of the debt.
	Aon Corporation entered into an agreement pursuant to which it agreed to guarantee the obligations of Aon plc arising under the 4.250% Notes due 2042 exchanged for Aon Corporation's outstanding 8.205% Notes due January 2027. Those Notes are subject to Rule 3-10 of Regulation S-X. Aon Corporation also agreed to guarantee the obligations of Aon plc arising under the 4.45% Notes due 2043, the 4.00% Notes due November 2023, the 2.875% Notes due May 2026, the 3.50% Notes due June 2024, and the 4.60% Notes due June 2044. In each case, the guarantee of Aon Corporation is full and unconditional. There are no subsidiaries of Aon plc, other than Aon Corporation, that are guarantors of the 4.250% Notes due 2042, the 4.45% Notes due 2043, the 4.00% Notes due 2023, the 2.875% Notes due 2026, the 3.50% Notes due 2024 or the 4.60% Notes due 2044.
	The following tables set forth condensed consolidating statements of income for the three and nine months ended September 30, 2014 and 2013, condensed consolidating statements of comprehensive income for the three and nine months ended September 30, 2014 and 2013, condensed consolidating statements of financial position as of September 30, 2014 and December 31, 2013, and condensed consolidating statements of cash flows for the nine months ended September 30, 2014 and 2013 in accordance with Rule 3-10 of Regulation S-X. The condensed consolidating financial information includes the accounts of Aon plc, the accounts of Aon Corporation, and the combined accounts of the non-guarantor subsidiaries. The condensed consolidating financial statements are presented in all periods as a merger under common control, with Aon plc presented as the parent company in all periods prior and subsequent to the Redomestication. The principal consolidating adjustments are to eliminate the investment in subsidiaries and intercompany balances and transactions.
	Condensed Consolidating Statement of Income
		Three months ended September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Revenue
	Commissions, fees and other	$	—		$	—		$	2,873		$	—		$	2,873
	Fiduciary investment income	—			—			7			—			7
	Total revenue	—			—			2,880			—			2,880
	Expenses
	Compensation and benefits	4			5			1,698			—			1,707
	Other general expenses	6			14			736			—			756
	Total operating expenses	10			19			2,434			—			2,463
	Operating (loss) income	(10		)	(19		)	446			—			417
	Interest income	(2		)	1			4			—			3
	Interest expense	(25		)	(42		)	2			—			(65		)
	Intercompany interest income (expense)	113			(73		)	(40		)	—			—
	Other income	2			2			31			—			35
	Income (loss) before taxes	78			(131		)	443			—			390
	Income tax expense (benefit)	16			(52		)	111			—			75
	Income (loss) before equity in earnings of subsidiaries	62			(79		)	332			—			315
	Equity in earnings of subsidiaries, net of tax	247			202			—			(449		)	—
	Net income	309			123			332			(449		)	315
	Less: Net income attributable to noncontrolling interests	—			—			6			—			6
	Net income attributable to Aon shareholders	$	309		$	123		$	326		$	(449	)	$	309
	Condensed Consolidating Statement of Income
		Three months ended September 30, 2013
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Revenue
	Commissions, fees and other	$	1		$	—		$	2,785		$	—		$	2,786
	Fiduciary investment income	—			—			8			—			8
	Total revenue	1			—			2,793			—			2,794
	Expenses
	Compensation and benefits	11			14			1,641			—			1,666
	Other general expenses	—			5			759			—			764
	Total operating expenses	11			19			2,400			—			2,430
	Operating (loss) income	(10		)	(19		)	393			—			364
	Interest income	—			1			2			—			3
	Interest expense	(6		)	(39		)	(8		)	—			(53		)
	Intercompany interest income (expense)	25			11			(36		)	—			—
	Other income	—			13			26			—			39
	Income (loss) before taxes	9			(33		)	377			—			353
	Income tax (benefit) expense	(2		)	(14		)	105			—			89
	Income (loss) before equity in earnings of subsidiaries	11			(19		)	272			—			264
	Equity in earnings of subsidiaries, net of tax	245			127			—			(372		)	—
	Net income	256			108			272			(372		)	264
	Less: Net income attributable to noncontrolling interests	—			—			8			—			8
	Net income attributable to Aon shareholders	$	256		$	108		$	264		$	(372	)	$	256
	Condensed Consolidating Statement of Income
		Nine months ended September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Revenue
	Commissions, fees and other	$	—		$	—		$	8,727		$	—		$	8,727
	Fiduciary investment income	—			—			19			—			19
	Total revenue	—			—			8,746			—			8,746
Expenses
Compensation and benefits	29			19			5,118			—			5,166
Other general expenses	18			37			2,194			—			2,249
Total operating expenses	47			56			7,312			—			7,415
Operating (loss) income	(47		)	(56		)	1,434			—			1,331
Interest income	(6		)	1			12			—			7
Interest expense	(49		)	(105		)	(34		)	—			(188		)
Intercompany interest income (expense)	335			(220		)	(115		)	—			—
Other income	1			10			23			—			34
Income (loss) before taxes	234			(370		)	1,320			—			1,184
Income tax expense (benefit)	49			(144		)	315			—			220
Income (loss) before equity in earnings of subsidiaries	185			(226		)	1,005			—			964
Equity in earnings of subsidiaries, net of tax	753			734			—			(1,487		)	—
Net income	938			508			1,005			(1,487		)	964
Less: Net income attributable to noncontrolling interests	—			—			26			—			26
Net income attributable to Aon shareholders	$	938		$	508		$	979		$	(1,487	)	$	938
Condensed Consolidating Statement of Income
	Nine months ended September 30, 2013
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
Revenue
Commissions, fees and other	$	2		$	—		$	8,583		$	—		$	8,585
Fiduciary investment income	—			—			21			—			21
Total revenue	2			—			8,604			—			8,606
Expenses
Compensation and benefits	27			34			5,042			—			5,103
Other general expenses	14			29			2,304			—			2,347
Total operating expenses	41			63			7,346			—			7,450
Operating (loss) income	(39		)	(63		)	1,258			—			1,156
Interest income	1			2			3			—			6
Interest expense	(12		)	(106		)	(35		)	—			(153		)
Intercompany interest (expense) income	11			96			(107		)	—			—
Other income	—			10			44			—			54
(Loss) income before taxes	(39		)	(61		)	1,163			—			1,063
Income tax (benefit) expense	(11		)	(24		)	310			—			275
(Loss) income before equity in earnings of subsidiaries	(28		)	(37		)	853			—			788
Equity in earnings of subsidiaries, net of tax	786			617			—			(1,403		)	—
Net income	758			580			853			(1,403		)	788
Less: Net income attributable to noncontrolling interests	—			—			30			—			30
Net income attributable to Aon shareholders	$	758		$	580		$	823		$	(1,403	)	$	758
Condensed Consolidating Statement of Comprehensive Income
	Three months ended September 30, 2014
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
Net income	$	309		$	123		$	332		$	(449	)	$	315
Less: Net income attributable to noncontrolling interests	—			—			6			—			6
Net income attributable to Aon shareholders	$	309		$	123		$	326		$	(449	)	$	309
Other comprehensive (loss) income, net of tax:
Change in fair value of investments	—			—			—			—			—
Change in fair value of derivatives	—			(1		)	(7		)	—			(8		)
Foreign currency translation adjustments	—			(17		)	(301		)	—			(318		)
Post-retirement benefit obligation	—			6			20			—			26
Total other comprehensive income	—			(12		)	(288		)	—			(300		)
Equity in other comprehensive loss of subsidiaries, net of tax	(300		)	(285		)	—			585			—
Less: Other comprehensive income attributable to noncontrolling interests	—			—			—			—			—
Total other comprehensive income attributable to Aon shareholders	(300		)	(297		)	(288		)	585			(300		)
Comprehensive income attributable to Aon shareholders	$	9		$	(174	)	$	38		$	136		$	9
Condensed Consolidating Statement of Comprehensive Income
	Three months ended September 30, 2013
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
Net income	$	256		$	108		$	272		$	(372	)	$	264
Less: Net income attributable to noncontrolling interests	—			—			8			—			8
Net income attributable to Aon shareholders	$	256		$	108		$	264		$	(372	)	$	256
Other comprehensive income (loss), net of tax:
Change in fair value of investments	—			(4		)	(10		)	—			(14		)
Change in fair value of derivatives	—			2			7			—			9
Foreign currency translation adjustments	—			6			149			—			155
Post-retirement benefit obligation	—			7			17			—			24
Total other comprehensive income	—			11			163			—			174
Equity in other comprehensive income of subsidiaries, net of tax	170			157			—			(327		)	—
Less: Other comprehensive income attributable to noncontrolling interests	—			—			3			—			3
Total other comprehensive income attributable to Aon shareholders	170			168			160			(327		)	171
Comprehensive income attributable to Aon Shareholders	$	426		$	276		$	424		$	(699	)	$	427
Condensed Consolidating Statement of Comprehensive Income
	Nine months ended September 30, 2014
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
Net income	$	938		$	508		$	1,005		$	(1,487	)	$	964
Less: Net income attributable to noncontrolling interests	—			—			26			—			26
Net income attributable to Aon shareholders	$	938		$	508		$	979		$	(1,487	)	$	938
Other comprehensive (loss) income, net of tax:
Change in fair value of investments	—			—			(1		)	—			(1		)
Change in fair value of derivatives	—			(1		)	14			—			13
Foreign currency translation adjustments	—			(19		)	(209		)	—			(228		)
Post-retirement benefit obligation	—			17			53			—			70
Total other comprehensive income	—			(3		)	(143		)	—			(146		)
Equity in other comprehensive loss of subsidiaries, net of tax	(144		)	(142		)	—			286			—
Less: Other comprehensive income attributable to noncontrolling interests	—			—			(2		)	—			(2		)
Total other comprehensive income attributable to Aon shareholders	(144		)	(145		)	(141		)	286			(144		)
Comprehensive income attributable to Aon shareholders	$	794		$	363		$	838		$	(1,201	)	$	794
Condensed Consolidating Statement of Comprehensive Income
	Nine months ended September 30, 2013
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
Net income	$	758		$	580		$	853		$	(1,403	)	$	788
Less: Net income attributable to noncontrolling interests	—			—			30			—			30
Net income attributable to Aon shareholders	$	758		$	580		$	823		$	(1,403	)	$	758
Other comprehensive income (loss), net of tax:
Change in fair value of investments	—			—			(1		)	—			(1		)
Change in fair value of derivatives	—			5			(17		)	—			(12		)
Foreign currency translation adjustments	—			(14		)	(63		)	—			(77		)
Post-retirement benefit obligation	—			22			43			—			65
Total other comprehensive income	—			13			(38		)	—			(25		)
Equity in other comprehensive income of subsidiaries, net of tax	(27		)	(38		)	—			65			—
Less: Other comprehensive income attributable to noncontrolling interests	—			—			1			—			1
Total other comprehensive income attributable to Aon shareholders	(27		)	(25		)	(39		)	65			(26		)
Comprehensive income attributable to Aon Shareholders	$	731		$	555		$	784		$	(1,338	)	$	732
Condensed Consolidating Statement of Financial Position
	As of September 30, 2014
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
ASSETS
Cash and cash equivalents	$	—		$	568		$	1,444		$	(1,630	)	$	382
Short-term investments	—			59			158			—			217
Receivables, net	—			—			2,633			(3		)	2,630
Fiduciary assets	—			—			10,815			—			10,815
Intercompany receivables	321			2,696			9,419			(12,436		)	—
Other current assets	1			205			669			(164		)	711
Total Current Assets	322			3,528			25,138			(14,233		)	14,755
Goodwill	—			—			9,026			—			9,026
Intangible assets, net	—			—			2,612			—			2,612
Fixed assets, net	—			—			760			—			760
Investments	—			79			64			—			143
Intercompany receivables	7,408			2,162			2,211			(11,781		)	—
Other non-current assets	169			498			1,550			(686		)	1,531
Investment in subsidiary	5,752			16,469			—			(22,221		)	—
TOTAL ASSETS	$	13,651		$	22,736		$	41,361		$	(48,921	)	$	28,827
LIABILITIES AND EQUITY
Fiduciary liabilities	$	—		$	—		$	10,815		$	—		$	10,815
Short-term debt and current portion of long-term debt	—			649			11			—			660
Accounts payable and accrued liabilities	1,683			34			1,444			(1,633		)	1,528
Intercompany payables	8			9,258			3,170			(12,436		)	—
Other current liabilities	72			47			898			(164		)	853
Total Current Liabilities	1,763			9,988			16,338			(14,233		)	13,856
Long-term debt	2,568			1,917			355			—			4,840
Pension, other post-retirement and other post-employment liabilities	—			854			583			—			1,437
Intercompany payables	2,100			7,277			2,404			(11,781		)	—
Other non-current liabilities	5			108			1,995			(686		)	1,422
TOTAL LIABILITIES	6,436			20,144			21,675			(26,700		)	21,555
TOTAL AON SHAREHOLDERS' EQUITY	7,215			2,592			19,629			(22,221		)	7,215
Noncontrolling interests	—			—			57			—			57
TOTAL EQUITY	7,215			2,592			19,686			(22,221		)	7,272
TOTAL LIABILITIES AND EQUITY	$	13,651		$	22,736		$	41,361		$	(48,921	)	$	28,827
Condensed Consolidating Statement of Financial Position
	As of December 31, 2013
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
ASSETS
Cash and cash equivalents	$	—		$	247		$	1,246		$	(1,016	)	$	477
Short-term investments	—			163			360			—			523
Receivables, net	—			4			2,892			—			2,896
Fiduciary assets	—			—			11,871			—			11,871
Intercompany receivables	186			3,503			5,452			(9,141		)	—
Other current assets	—			69			513			(19		)	563
Total Current Assets	186			3,986			22,334			(10,176		)	16,330
Goodwill	—			—			8,997			—			8,997
Intangible assets, net	—			—			2,578			—			2,578
Fixed assets, net	—			—			791			—			791
Investments	—			57			75			—			132
Intercompany receivables	7,166			2,178			2,201			(11,545		)	—
Other non-current assets	146			560			1,421			(704		)	1,423
Investment in subsidiary	4,607			11,694			—			(16,301		)	—
TOTAL ASSETS	$	12,105		$	18,475		$	38,397		$	(38,726	)	$	30,251
LIABILITIES AND EQUITY
Fiduciary liabilities	$	—		$	—		$	11,871		$	—		$	11,871
Short-term debt and current portion of long-term debt	—			—			707			(4		)	703
Accounts payable and accrued liabilities	1,036			62			1,849			(1,016		)	1,931
Intercompany payables	15			5,449			3,677			(9,141		)	—
Other current liabilities	12			47			866			(19		)	906
Total Current Liabilities	1,063			5,558			18,970			(10,180		)	15,411
Long-term debt	792			2,512			378			4			3,686
Pension, other post-retirement and other post-employment liabilities	—			925			682			—			1,607
Intercompany payables	2,100			7,267			2,178			(11,545		)	—
Other non-current liabilities	5			159			1,892			(704		)	1,352
TOTAL LIABILITIES	3,960			16,421			24,100			(22,425		)	22,056
TOTAL AON SHAREHOLDERS' EQUITY	8,145			2,054			14,247			(16,301		)	8,145
Noncontrolling interests	—			—			50			—			50
TOTAL EQUITY	8,145			2,054			14,297			(16,301		)	8,195
TOTAL LIABILITIES AND EQUITY	$	12,105		$	18,475		$	38,397		$	(38,726	)	$	30,251
Condensed Consolidating Statement of Cash Flows
	Nine months ended September 30, 2014
	Aon			Aon			Other			Consolidating
							Non-Guarantor
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
CASH FLOWS FROM OPERATING ACTIVITIES
CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	$	309		$	(348	)	$	922		$	—		$	883
CASH FLOWS FROM INVESTING ACTIVITIES
Sales of long-term investments	—			39			12			—			51
Purchase of long-term investments	—			(19		)	—			—			(19		)
Net sales of short-term investments - non-fiduciary	—			103			198			—			301
Acquisition of businesses, net of cash acquired	—			—			(464		)	—			(464		)
Proceeds from sale of businesses	—			—			48			—			48
Capital expenditures	—			—			(179		)	—			(179		)
CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	—			123			(385		)	—			(262		)
CASH FLOWS FROM FINANCING ACTIVITIES
Share repurchase	(1,750		)	—			—			—			(1,750		)
Advances (to) from affiliates	(253		)	496			371			(614		)	—
Issuance of shares for employee benefit plans	58			—			—			—			58
Issuance of debt	2,714			1,541			—			—			4,255
Repayment of debt	(877		)	(1,491		)	(705		)	—			(3,073		)
Cash dividends to shareholders	(201		)	—			—			—			(201		)
Purchase of shares from noncontrolling interests	—			—			1			—			1
Dividends paid to noncontrolling interests	—			—			(18		)	—			(18		)
Proceeds from sale-leaseback	—			—			25			—			25
CASH (USED FOR) PROVIDED BY FINANCING ACTIVITIES	(309		)	546			(326		)	(614		)	(703		)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	—			—			(13		)	—			(13		)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	—			321			198			(614		)	(95		)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	—			247			1,246			(1,016		)	477
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$	—		$	568		$	1,444		$	(1,630	)	$	382
Condensed Consolidating Statement of Cash Flows
	Nine months ended September 30, 2013
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
CASH FLOWS FROM OPERATING ACTIVITIES
CASH (USED FOR) PROVIDED BY OPERATING ACTIVITIES	$	(14	)	$	(195	)	$	1,193		$	—		$	984
CASH FLOWS FROM INVESTING ACTIVITIES
Sales of long-term investments	—			8			73			—			81
Purchase of long-term investments	—			(13		)	—			—			(13		)
Net sales of short-term investments - non-fiduciary	—			(35		)	22			—			(13		)
Acquisition of businesses, net of cash acquired	—			—			(26		)	—			(26		)
Proceeds from sale of businesses	—			—			6			—			6
Capital expenditures	—			—			(174		)	—			(174		)
CASH USED FOR INVESTING ACTIVITIES	—			(40		)	(99		)	—			(139		)
CASH FLOWS FROM FINANCING ACTIVITIES
Share repurchase	(1,025		)	—			—			—			(1,025		)
Advances from (to) affiliates	405			610			(1,014		)	(1		)	—
Issuance of shares for employee benefit plans	84			—			—			—			84
Issuance of debt	1,145			2,894			231			—			4,270
Repayment of debt	(449		)	(3,177		)	(244		)	—			(3,870		)
Cash dividends to shareholders	(159		)	—			—			—			(159		)
Purchase of shares from noncontrolling interests	—			—			(6		)	—			(6		)
Dividends paid to noncontrolling interests	—			—			(13		)	—			(13		)
CASH PROVIDED BY (USED FOR)	1			327			(1,046		)	(1		)	(719		)
FINANCING ACTIVITIES
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	—			—			(48		)	—			(48		)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(13		)	92			—			(1		)	78
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	131			199			—			(39		)	291
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$	118		$	291		$	—		$	(40	)	$	369

Other_Financial_Data_Tables

Other Financial Data (Tables)	9 Months Ended
	Sep. 30, 2014
Other Financial Data [Abstract]	'
Schedule of Other Income	'
	Other income consists of the following (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Equity earnings	$	4		$	6		$	10		$	12
	Gain on investments	4			37			2			36
	Foreign currency remeasurement gain (loss)	7			(4		)	11			15
	Derivative (loss) gain	(6		)	1			(19		)	(8		)
	Gain on disposal of business	25			—			25			—
	Other	1			(1		)	5			(1		)
		$	35		$	39		$	34		$	54
Schedule of Allowance for Doubtful Accounts	'
	An analysis of the allowance for doubtful accounts is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Balance at beginning of period	$	88		$	114		$	90		$	118
	Provision charged to operations	1			(5		)	9			6
	Accounts written off, net of recoveries	(14		)	(8		)	(23		)	(26		)
	Effect of exchange rate changes and other	4			(2		)	3			1
	Balance at end of period	$	79		$	99		$	79		$	99
Schedule of Other Current Assets	'
	The components of Other current assets are as follows (in millions):
		September 30, 2014			December 31, 2013
	Taxes receivable	258			111
	Prepaid expenses	238			229
	Deferred project costs	102			98
	Deferred tax assets	81			93
	Other	32			32
		$	711		$	563
Schedule of Other Non-current Assets	'
	The components of Other non-current assets are as follows (in millions):
		September 30, 2014			December 31, 2013
	Prepaid pension (1)	$	750		$	567
	Deferred project costs	256			273
	Deferred tax assets	176			193
	Taxes receivable	98			108
	Other	251			282
		$	1,531		$	1,423
	______________________________________________
	-1	Increase in prepaid pensions is primarily due to cash funding of the U.K. pension plans.
Schedule of Other Current Liabilities	'
	The components of Other current liabilities are as follows (in millions):
		September 30, 2014			December 31, 2013
	Deferred revenue	$	440		$	475
	Taxes payable	96			136
	Deferred tax liabilities	36			48
	Other	281			247
		$	853		$	906
Schedule of Other Non-current Liabilities	'
	The components of Other non-current liabilities are as follows (in millions):
		September 30, 2014			December 31, 2013
	Deferred tax liabilities	$	535		$	420
	Taxes payable	202			184
	Leases	191			204
	Deferred revenue	170			134
	Compensation and benefits	56			105
	Other	268			305
		$	1,422		$	1,352

Acquisitions_and_Dispositions_

Acquisitions and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]	'
Consideration transferred and preliminary value of intangible assets	'
	The following table includes the aggregate consideration transferred and the preliminary value of intangible assets recorded as a result of the Company's acquisitions (in millions):
		Nine months ended September 30,
		2014		2013
	Consideration	$	446	$	26
	Intangible assets:
	Goodwill	$	261	$	26
	Other intangible assets	310		8
	Total	$	571	$	34

Goodwill_and_Other_Intangible_1

Goodwill and Other Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Schedule of changes in the net carrying amount of goodwill by operating segment	'
	The changes in the net carrying amount of goodwill by reportable segment for the nine months ended September 30, 2014 are as follows (in millions):
		Risk			HR			Total
		Solutions			Solutions
	Balance as of December 31, 2013	$	6,020		$	2,977		$	8,997
	Goodwill related to current year acquisitions	256			5			261
	Goodwill related to disposals	(14		)	—			(14		)
	Goodwill related to prior year acquisitions	(1		)	—			(1		)
	Transfer	(2		)	2			—
	Foreign currency translation	(202		)	(15		)	(217		)
	Balance as of September 30, 2014	$	6,057		$	2,969		$	9,026
Schedule of other intangible assets by asset class	'
	Other intangible assets by asset class are as follows (in millions):
		September 30, 2014									December 31, 2013
		Gross Carrying Amount			Accumulated			Net Carrying Amount			Gross Carrying Amount		Accumulated		Net Carrying Amount
					Amortization								Amortization
	Intangible assets with indefinite lives:
	Tradenames	$	1,019		$	—		$	1,019		$	1,019	$	—	$	1,019
	Intangible assets with finite lives:
	Customer related and contract based	2,972			1,520			1,452			2,720		1,310		1,410
	Marketing, technology and other	588			447			141			584		435		149
		$	4,579		$	1,967		$	2,612		$	4,323	$	1,745	$	2,578
Schedule of estimated future amortization expense on intangible assets	'
	The estimated future amortization for finite lived intangible assets as of September 30, 2014 is as follows (in millions):
		Risk Solutions			HR Solutions			Total
	Remainder of 2014	$	29		$	60		$	89
	2015	109			211			320
	2016	100			176			276
	2017	91			140			231
	2018	79			93			172
	Thereafter	253			252			505
		$	661		$	932		$	1,593

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Schedule of interest bearing assets	'
	The Company's interest-bearing assets and other investments are included in the following categories in the Condensed Consolidated Statements of Financial Position (in millions):
		September 30,		December 31,
		2014		2013
	Cash and cash equivalents	$	382	$	477
	Short-term investments	217		523
	Fiduciary assets (1)	3,877		3,778
	Investments	143		132
		$	4,619	$	4,910
	______________________________________________
	-1	Fiduciary assets include funds held on behalf of clients but does not include fiduciary receivables.
Schedule of investments	'
	The Company's investments are as follows (in millions):
		September 30,		December 31,
		2014		2013
	Equity method investments	$	122	$	113
	Other investments	13		10
	Fixed-maturity securities	8		9
		$	143	$	132

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Schedule of components of weighted average number of shares	'
	Weighted average shares outstanding are as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014		2013
	Shares for basic earnings per share (1)	292.3			309.5			298.1		313.2
	Common stock equivalents	3.8			3.4			3.5		3.5
	Shares for diluted earnings per share	296.1			312.9			301.6		316.7
	______________________________________________
	(1) Includes 2.9 million and 3.8 million of participating securities for the three months ended September 30, 2014 and 2013, respectively, and 3.1 million and 4.0 million of participating securities for the nine months ended September 30, 2014 and 2013, respectively.
Components of Accumulated other comprehensive loss, net of related tax	'
	Changes in Accumulated other comprehensive loss by component, net of related tax, are as follows (in millions):
		Change in Fair Value of Investments (1)				Change in Fair Value of Derivatives (1)			Foreign Currency Translation Adjustments			Post-Retirement Benefit Obligation (2)			Total
	Balance at December 31, 2013	$	1			$	(22	)	$	169		$	(2,522	)	$	(2,374	)
	Other comprehensive (loss) income before reclassifications, net	(1		)		1			(226		)	2			(224		)
	Amounts reclassified from accumulated other comprehensive loss:
	Amounts reclassified from accumulated other comprehensive loss	—				17			—			94			111
	Tax benefit	—				(5		)	—			(26		)	(31		)
	Amounts reclassified from accumulated other comprehensive loss, net	—				12			—			68			80
	Net current period other comprehensive (loss) income	(1		)		13			(226		)	70			(144		)
	Balance at September 30, 2014	$	—			$	(9	)	$	(57	)	$	(2,452	)	$	(2,518	)
	______________________________________________
	(1) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Other income.
	(2) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Compensation and benefits

Employee_Benefits_Tables

Employee Benefits (Tables)	9 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Components of net periodic benefit cost for the pension plans	'
	The following table provides the components of the net periodic benefit cost for Aon's material U.K., U.S., and other significant international pension plans, which are located in the Netherlands and Canada (in millions):
		Three months ended September 30,
		U.K.						U.S.						Other
		2014			2013			2014			2013			2014			2013
	Service cost	$	—		$	—		$	—		$	—		$	—		$	5
	Interest cost	58			52			32			28			12			11
	Expected return on plan assets	(82		)	(74		)	(39		)	(34		)	(15		)	(15		)
	Amortization of net actuarial loss	13			12			11			13			2			6
	Total net periodic (benefit) cost	$	(11	)	$	(10	)	$	4		$	7		$	(1	)	$	7
		Nine months ended September 30,
		U.K.						U.S.						Other
		2014			2013			2014			2013			2014			2013
	Service cost	$	—		$	—		$	—		$	—		$	—		$	14
	Interest cost	174			156			96			84			36			33
	Expected return on plan assets	(247		)	(223		)	(117		)	(103		)	(45		)	(44		)
	Amortization of net actuarial loss	40			36			32			39			6			19
	Net periodic (benefit) cost	(33		)	(31		)	11			20			(3		)	22
	Curtailment loss (gain) and other	—			—			1			—			(3		)	—
	Total net periodic (benefit) cost	$	(33	)	$	(31	)	$	12		$	20		$	(6	)	$	22

ShareBased_Compensation_Plans_

Share-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-based compensation expense recognized in continuing operations	'
	The following table summarizes share-based compensation expense recognized in the Condensed Consolidated Statements of Income in Compensation and benefits (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014				2013
	Restricted share units ("RSUs")	$	41		$	40		$	144			$	135
	Performance share awards ("PSAs")	29			28			96				66
	Share options	—			—			—				1
	Employee share purchase plans	2			2			7				5
	Total share-based compensation expense	$	72		$	70		$	247			$	207
Restricted share unit activity	'
	A summary of the status of the Company's RSUs is as follows (shares in thousands):
		Nine months ended September 30,
		2014					2013
		Shares		Fair Value (1)			Shares			Fair Value (1)
	Non-vested at beginning of period	9,759		$	51		10,432			$	44
	Granted	2,675		84			3,598			62
	Vested	(3,561	)	49			(3,618	)		44
	Forfeited	(385	)	56			(308	)		47
	Non-vested at end of period	8,488		63			10,104			51
	______________________________________________
	-1	Represents per share weighted average fair value of award at date of grant.
Performance-based plans	'
	Information as of September 30, 2014 regarding the Company's target PSAs granted and shares that would be issued at current performance levels for PSAs granted during the nine months ended September 30, 2014 and the years ended December 31, 2013 and 2012, respectively, is as follows (shares in thousands, dollars in millions, except fair value):
		As of September 30, 2014			As of December 31, 2013			As of December 31, 2012
	Target PSAs granted	816			1,135			1,369
	Fair value (1)	$	81		$	58		$	47
	Number of shares that would be issued based on current performance levels	804			2,211			2,656
	Unamortized expense, based on current performance levels	$	52		$	57		$	11
	______________________________________________
	-1	Represents per share weighted average fair value of award at date of grant.
Share options and related information	'
	A summary of the status of the Company's share options and related information is as follows (shares in thousands):
		Nine months ended September 30,
		2014					2013
		Shares		Weighted- Average			Shares			Weighted- Average
				Exercise Price						Exercise Price
	Beginning outstanding	3,462		$	32		5,611			$	32
	Granted	—		—			—			—
	Exercised	(953	)	32			(1,694	)		32
	Forfeited and expired	(6	)	37			(29	)		34
	Outstanding at end of period	2,503		32			3,888			32
	Exercisable at end of period	2,464		32			3,681			32
Other information related to the company's share options	'
	Other information related to the Company's share options is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014				2013
	Aggregate intrinsic value of stock options exercised	$	6		$	14		$	51			$	53
	Cash received from the exercise of stock options	3			14			30				55
	Tax benefit realized from the exercise of stock options	2			3			14				10

Derivatives_and_Hedging_Tables

Derivatives and Hedging (Tables)	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Notional and fair values of derivative instruments	'
	The notional and fair values of derivative instruments are as follows (in millions):
		Notional Amount						Derivative Assets (1)						Derivative Liabilities (2)
		September 30,			December 31,			September 30,			December 31,			September 30,			December 31,
		2014			2013			2014			2013			2014			2013
	Derivatives accounted for as hedges:
	Interest rate contracts	$	—		$	171		$	—		$	9		$	—		$	—
	Foreign exchange contracts	1,106			1,191			55			71			65			93
	Total	1,106			1,362			55			80			65			93
	Derivatives not accounted for as hedges:
	Foreign exchange contracts	184			215			—			—			—			—
	Total	$	1,290		$	1,577		$	55		$	80		$	65		$	93
	______________________________________________
	-1	Included within Other current assets ($25 million and $46 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current assets ($30 million and $34 million at September 30, 2014 and December 31, 2013, respectively).
	-2	Included within Other current liabilities ($17 million and $51 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current liabilities ($48 million and $42 million at September 30, 2014 and December 31, 2013, respectively).
	Offsetting of financial assets and derivatives assets are as follows (in millions):
		Gross Amounts of Recognized Assets						Gross Amounts Offset in the Statement of Financial Position						Net Amounts of Assets Presented in the Statement of Financial Position (1)
		September 30,			December 31,			September 30,			December 31,			September 30,			December 31,
		2014			2013			2014			2013			2014			2013
	Derivatives accounted for as hedges:
	Interest rate contracts	$	—		$	9		$	—		$	—		$	—		$	9
	Foreign exchange contracts	55			71			(15		)	(30		)	40			41
	Total	55			80			(15		)	(30		)	40			50
	Derivatives not accounted for as hedges:
	Foreign exchange contracts	—			—			—			—			—			—
	Total	$	55		$	80		$	(15	)	$	(30	)	$	40		$	50
	______________________________________________
	(1) Included within Other current assets ($13 million and $18 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current assets ($27 million and $32 million at September 30, 2014 and December 31, 2013, respectively).
	Offsetting of financial liabilities and derivative liabilities are as follows (in millions):
		Gross Amounts of Recognized Liabilities						Gross Amounts Offset in the Statement of Financial Position						Net Amounts of Liabilities Presented in the Statement of Financial Position (1)
		September 30,			December 31,			September 30,			December 31,			September 30,			December 31,
		2014			2013			2014			2013			2014			2013
	Derivatives accounted for as hedges:
	Interest rate contracts	$	—		$	—		$	—		$	—		$	—		$	—
	Foreign exchange contracts	65			93			(15		)	(30		)	50			63
	Total	65			93			(15		)	(30		)	50			63
	Derivatives not accounted for as hedges:
	Foreign exchange contracts	—			—			—			—			—			—
	Total	$	65		$	93		$	(15	)	$	(30	)	$	50		$	63
	______________________________________________
	(1) Included within Other current liabilities ($5 million and $23 million at September 30, 2014 and December 31, 2013, respectively) or Other non-current liabilities ($45 million and $40 million at September 30, 2014 and December 31, 2013, respectively)
Derivative gains (losses)	'
	The amounts of derivative gains (losses) recognized in the Condensed Consolidated Financial Statements for the three and nine months ended September 30, 2014 and 2013 are as follows (in millions):
	Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Cash flow hedges:
	Interest rate contracts (1)	$	—		$	—		$	—		$	—
	Foreign exchange contracts (2)	(3		)	—			4			(28		)
	Total	$	(3	)	$	—		$	4		$	(28	)
	______________________________________________
	(1) Location of future reclassification from Accumulated Other Comprehensive Loss will be included within Interest expense.
	(2) Location of future reclassification from Accumulated Other Comprehensive Loss will be included within Compensation and benefits ($2 million and $3 million loss for the three months ended September 30, 2014 and 2013, respectively, and $14 million gain and $17 million loss for the nine months ended September 30, 2014 and 2013, respectively), Other income ($2 million and $3 million gain for the three months ended September 30, 2014 and 2013, respectively, and $9 million and $11 million loss for the nine months ended September 30, 2014 and 2013, respectively), and Other general expenses ($3 million and $1 million loss for the three and nine months ended September 30, 2014, respectively).
	Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Cash flow hedges:
	Interest rate contracts (1)	$	—		$	—		$	(1	)	$	(1	)
	Foreign exchange contracts (2)	4			(10		)	(15		)	(7		)
	Total	4			(10		)	(16		)	(8		)
	______________________________________________
	(1) Included within Interest expense
	(2) Included within Compensation and benefits ($1 million and $5 million loss for the three months ended September 30, 2014 and 2013, respectively, and $4 million and $9 million loss for the nine months ended September 30, 2014 and 2013, respectively), Other income ($5 million gain and $5 million loss for the three months ended September 30, 2014 and 2013, respectively, and $6 million loss and $3 million gain for the nine months ended September 30, 2014 and 2013, respectively), Interest expenses ($3 million and $8 million loss for the three and nine months ended September 30, 2014, respectively), and Other general expenses ($3 million gain for the three months ended September 30, 2014, and $3 million gain and $1 million loss for the nine months ended September 30, 2014 and 2013, respectively).
	The amount of gain (loss) recognized in the Condensed Consolidated Financial Statements is as follows (in millions):
		Three months ended September 30,												Nine months ended September 30,
		Amount of Gain (Loss) Recognized in Income on Derivative (1)						Amount of Gain (Loss) Recognized in Income on Related Hedged Item						Amount of Gain (Loss) Recognized in Income on Derivative (1) (2)						Amount of Gain (Loss) Recognized in Income on Related Hedge Item (1) (2)
		2014			2013			2014			2013			2014			2013			2014		2013
	Fair value hedges:
	Foreign exchange contracts (2)	$	(9	)	$	(7	)	$	9		$	7		$	(9	)	$	(8	)	$	9	$	8
	______________________________________________
	(1) Included in Interest expense.
	(2) Relates to fixed rate debt.

Fair_Value_Measurements_and_Fi1

Fair Value Measurements and Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule of assets and liabilities that are measured at fair value on a recurring basis	'
	The following tables present the categorization of the Company's assets and liabilities that are measured at fair value on a recurring basis at September 30, 2014 and December 31, 2013 (in millions):
				Fair Value Measurements Using
		Balance at September 30, 2014		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	Assets:
	Money market funds and highly liquid debt securities (1)	$	1,649	$	1,647	$	2	$	—
	Other investments:
	Fixed maturity securities:
	Corporate bonds	1		—		—		1
	Government bonds	7		—		7		—
	Equity securities	11		6		5		—
	Derivatives:
	Interest rate contracts	—		—		—		—
	Foreign exchange contracts	55		—		55		—
	Liabilities:
	Derivatives:
	Foreign exchange contracts	65		—		65		—
	______________________________________________
	(1) Includes $1,647 million of money market funds and $2 million of highly liquid debt securities that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity.  See Note 8 "Investments" for additional information regarding the Company's investments.
				Fair Value Measurements Using
		Balance at December 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	Assets:
	Money market funds and highly liquid debt securities (1)	$	2,079	$	2,054	$	25	$	—
	Other investments:
	Fixed maturity securities:
	Corporate bonds	2		—		—		2
	Government bonds	7		—		7		—
	Equity securities	13		6		7		—
	Derivatives:
	Interest rate contracts	9		—		9		—
	Foreign exchange contracts	71		—		71		—
	Liabilities:
	Derivatives:
	Foreign exchange contracts	93		—		93		—
	______________________________________________
	(1)  Includes $2,054 million of money market funds and $25 million of highly liquid debt securities that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity.  See Note 8 "Investments" for additional information regarding the Company's investments.
Schedule of financial instruments where the carrying amounts and fair values differ	'
	The fair value of Long-term debt is classified as Level 2 of the fair value hierarchy. The following table discloses the Company's financial instruments where the carrying amounts and fair values differ (in millions):
		September 30, 2014				December 31, 2013
		Carrying Value		Fair Value		Carrying Value		Fair Value
	Long-term debt	$	4,840	$	5,190	$	3,686	$	3,894

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Schedule of total revenue by business segments	'
	Aon's total revenue is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Risk Solutions	$	1,836		$	1,821		$	5,778		$	5,736
	HR Solutions	1,057			981			3,004			2,891
	Intersegment eliminations	(13		)	(8		)	(36		)	(21		)
	Total revenue	$	2,880		$	2,794		$	8,746		$	8,606
Schedule of commissions, fees and other revenues by products	'
	Commissions, fees and other revenues by product are as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Retail brokerage	$	1,458		$	1,424		$	4,619		$	4,548
	Reinsurance brokerage	371			389			1,140			1,167
	Total Risk Solutions Segment	1,829			1,813			5,759			5,715
	Consulting services	466			406			1,245			1,176
	Outsourcing	604			587			1,788			1,746
	Intrasegment	(13		)	(12		)	(29		)	(31		)
	Total HR Solutions Segment	1,057			981			3,004			2,891
	Intersegment	(13		)	(8		)	(36		)	(21		)
	Total commissions, fees and other revenue	$	2,873		$	2,786		$	8,727		$	8,585
Schedule of fiduciary investment income by business segments	'
	Fiduciary investment income by segment is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Risk Solutions	$	7		$	8		$	19		$	21
	HR Solutions	—			—			—			—
	Total fiduciary investment income	$	7		$	8		$	19		$	21
Schedule of reconciliation of segment income before tax to income from continuing operations before income taxes	'
	A reconciliation of segment operating income before tax to income before income taxes is as follows (in millions):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Risk Solutions	$	343		$	333		$	1,205		$	1,127
	HR Solutions	113			75			249			162
	Segment income before income taxes	456			408			1,454			1,289
	Unallocated expenses	(39		)	(44		)	(123		)	(133		)
	Interest income	3			3			7			6
	Interest expense	(65		)	(53		)	(188		)	(153		)
	Other income	35			39			34			54
	Income before income taxes	$	390		$	353		$	1,184		$	1,063

Guarantee_of_Registered_Securi1

Guarantee of Registered Securities (Tables)	9 Months Ended
	Sep. 30, 2014
Guarantee of Registered Securities [Abstract]	'
Condensed Consolidating Statements of Income	'
	Condensed Consolidating Statement of Income
		Three months ended September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Revenue
	Commissions, fees and other	$	—		$	—		$	2,873		$	—		$	2,873
	Fiduciary investment income	—			—			7			—			7
	Total revenue	—			—			2,880			—			2,880
	Expenses
	Compensation and benefits	4			5			1,698			—			1,707
	Other general expenses	6			14			736			—			756
	Total operating expenses	10			19			2,434			—			2,463
	Operating (loss) income	(10		)	(19		)	446			—			417
	Interest income	(2		)	1			4			—			3
	Interest expense	(25		)	(42		)	2			—			(65		)
	Intercompany interest income (expense)	113			(73		)	(40		)	—			—
	Other income	2			2			31			—			35
	Income (loss) before taxes	78			(131		)	443			—			390
	Income tax expense (benefit)	16			(52		)	111			—			75
	Income (loss) before equity in earnings of subsidiaries	62			(79		)	332			—			315
	Equity in earnings of subsidiaries, net of tax	247			202			—			(449		)	—
	Net income	309			123			332			(449		)	315
	Less: Net income attributable to noncontrolling interests	—			—			6			—			6
	Net income attributable to Aon shareholders	$	309		$	123		$	326		$	(449	)	$	309
	Condensed Consolidating Statement of Income
		Three months ended September 30, 2013
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Revenue
	Commissions, fees and other	$	1		$	—		$	2,785		$	—		$	2,786
	Fiduciary investment income	—			—			8			—			8
	Total revenue	1			—			2,793			—			2,794
	Expenses
	Compensation and benefits	11			14			1,641			—			1,666
	Other general expenses	—			5			759			—			764
	Total operating expenses	11			19			2,400			—			2,430
	Operating (loss) income	(10		)	(19		)	393			—			364
	Interest income	—			1			2			—			3
	Interest expense	(6		)	(39		)	(8		)	—			(53		)
	Intercompany interest income (expense)	25			11			(36		)	—			—
	Other income	—			13			26			—			39
	Income (loss) before taxes	9			(33		)	377			—			353
	Income tax (benefit) expense	(2		)	(14		)	105			—			89
	Income (loss) before equity in earnings of subsidiaries	11			(19		)	272			—			264
	Equity in earnings of subsidiaries, net of tax	245			127			—			(372		)	—
	Net income	256			108			272			(372		)	264
	Less: Net income attributable to noncontrolling interests	—			—			8			—			8
	Net income attributable to Aon shareholders	$	256		$	108		$	264		$	(372	)	$	256
	Condensed Consolidating Statement of Income
		Nine months ended September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Revenue
	Commissions, fees and other	$	—		$	—		$	8,727		$	—		$	8,727
	Fiduciary investment income	—			—			19			—			19
	Total revenue	—			—			8,746			—			8,746
	Expenses
	Compensation and benefits	29			19			5,118			—			5,166
	Other general expenses	18			37			2,194			—			2,249
	Total operating expenses	47			56			7,312			—			7,415
Operating (loss) income	(47		)	(56		)	1,434			—			1,331
Interest income	(6		)	1			12			—			7
Interest expense	(49		)	(105		)	(34		)	—			(188		)
Intercompany interest income (expense)	335			(220		)	(115		)	—			—
Other income	1			10			23			—			34
Income (loss) before taxes	234			(370		)	1,320			—			1,184
Income tax expense (benefit)	49			(144		)	315			—			220
Income (loss) before equity in earnings of subsidiaries	185			(226		)	1,005			—			964
Equity in earnings of subsidiaries, net of tax	753			734			—			(1,487		)	—
Net income	938			508			1,005			(1,487		)	964
Less: Net income attributable to noncontrolling interests	—			—			26			—			26
Net income attributable to Aon shareholders	$	938		$	508		$	979		$	(1,487	)	$	938
Condensed Consolidating Statement of Income
	Nine months ended September 30, 2013
							Other
	Aon			Aon			Non-Guarantor			Consolidating
(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
Revenue
Commissions, fees and other	$	2		$	—		$	8,583		$	—		$	8,585
Fiduciary investment income	—			—			21			—			21
Total revenue	2			—			8,604			—			8,606
Expenses
Compensation and benefits	27			34			5,042			—			5,103
Other general expenses	14			29			2,304			—			2,347
Total operating expenses	41			63			7,346			—			7,450
Operating (loss) income	(39		)	(63		)	1,258			—			1,156
Interest income	1			2			3			—			6
Interest expense	(12		)	(106		)	(35		)	—			(153		)
Intercompany interest (expense) income	11			96			(107		)	—			—
Other income	—			10			44			—			54
(Loss) income before taxes	(39		)	(61		)	1,163			—			1,063
Income tax (benefit) expense	(11		)	(24		)	310			—			275
(Loss) income before equity in earnings of subsidiaries	(28		)	(37		)	853			—			788
Equity in earnings of subsidiaries, net of tax	786			617			—			(1,403		)	—
Net income	758			580			853			(1,403		)	788
Less: Net income attributable to noncontrolling interests	—			—			30			—			30
Net income attributable to Aon shareholders	$	758		$	580		$	823		$	(1,403	)	$	758
Condensed Consolidating Statements of Comprehensive Income	'
	Condensed Consolidating Statement of Comprehensive Income
		Three months ended September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Net income	$	309		$	123		$	332		$	(449	)	$	315
	Less: Net income attributable to noncontrolling interests	—			—			6			—			6
	Net income attributable to Aon shareholders	$	309		$	123		$	326		$	(449	)	$	309
	Other comprehensive (loss) income, net of tax:
	Change in fair value of investments	—			—			—			—			—
	Change in fair value of derivatives	—			(1		)	(7		)	—			(8		)
	Foreign currency translation adjustments	—			(17		)	(301		)	—			(318		)
	Post-retirement benefit obligation	—			6			20			—			26
	Total other comprehensive income	—			(12		)	(288		)	—			(300		)
	Equity in other comprehensive loss of subsidiaries, net of tax	(300		)	(285		)	—			585			—
	Less: Other comprehensive income attributable to noncontrolling interests	—			—			—			—			—
	Total other comprehensive income attributable to Aon shareholders	(300		)	(297		)	(288		)	585			(300		)
	Comprehensive income attributable to Aon shareholders	$	9		$	(174	)	$	38		$	136		$	9
	Condensed Consolidating Statement of Comprehensive Income
		Three months ended September 30, 2013
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Net income	$	256		$	108		$	272		$	(372	)	$	264
	Less: Net income attributable to noncontrolling interests	—			—			8			—			8
	Net income attributable to Aon shareholders	$	256		$	108		$	264		$	(372	)	$	256
	Other comprehensive income (loss), net of tax:
	Change in fair value of investments	—			(4		)	(10		)	—			(14		)
	Change in fair value of derivatives	—			2			7			—			9
	Foreign currency translation adjustments	—			6			149			—			155
	Post-retirement benefit obligation	—			7			17			—			24
	Total other comprehensive income	—			11			163			—			174
	Equity in other comprehensive income of subsidiaries, net of tax	170			157			—			(327		)	—
	Less: Other comprehensive income attributable to noncontrolling interests	—			—			3			—			3
	Total other comprehensive income attributable to Aon shareholders	170			168			160			(327		)	171
	Comprehensive income attributable to Aon Shareholders	$	426		$	276		$	424		$	(699	)	$	427
	Condensed Consolidating Statement of Comprehensive Income
		Nine months ended September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Net income	$	938		$	508		$	1,005		$	(1,487	)	$	964
	Less: Net income attributable to noncontrolling interests	—			—			26			—			26
	Net income attributable to Aon shareholders	$	938		$	508		$	979		$	(1,487	)	$	938
	Other comprehensive (loss) income, net of tax:
	Change in fair value of investments	—			—			(1		)	—			(1		)
	Change in fair value of derivatives	—			(1		)	14			—			13
	Foreign currency translation adjustments	—			(19		)	(209		)	—			(228		)
	Post-retirement benefit obligation	—			17			53			—			70
	Total other comprehensive income	—			(3		)	(143		)	—			(146		)
	Equity in other comprehensive loss of subsidiaries, net of tax	(144		)	(142		)	—			286			—
	Less: Other comprehensive income attributable to noncontrolling interests	—			—			(2		)	—			(2		)
	Total other comprehensive income attributable to Aon shareholders	(144		)	(145		)	(141		)	286			(144		)
	Comprehensive income attributable to Aon shareholders	$	794		$	363		$	838		$	(1,201	)	$	794
	Condensed Consolidating Statement of Comprehensive Income
		Nine months ended September 30, 2013
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	Net income	$	758		$	580		$	853		$	(1,403	)	$	788
	Less: Net income attributable to noncontrolling interests	—			—			30			—			30
	Net income attributable to Aon shareholders	$	758		$	580		$	823		$	(1,403	)	$	758
	Other comprehensive income (loss), net of tax:
Change in fair value of investments	—			—			(1		)	—			(1		)
Change in fair value of derivatives	—			5			(17		)	—			(12		)
Foreign currency translation adjustments	—			(14		)	(63		)	—			(77		)
Post-retirement benefit obligation	—			22			43			—			65
Total other comprehensive income	—			13			(38		)	—			(25		)
Equity in other comprehensive income of subsidiaries, net of tax	(27		)	(38		)	—			65			—
Less: Other comprehensive income attributable to noncontrolling interests	—			—			1			—			1
Total other comprehensive income attributable to Aon shareholders	(27		)	(25		)	(39		)	65			(26		)
Comprehensive income attributable to Aon Shareholders	$	731		$	555		$	784		$	(1,338	)	$	732
Condensed Consolidating Statements of Financial Position	'
	Condensed Consolidating Statement of Financial Position
		As of September 30, 2014
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	ASSETS
	Cash and cash equivalents	$	—		$	568		$	1,444		$	(1,630	)	$	382
	Short-term investments	—			59			158			—			217
	Receivables, net	—			—			2,633			(3		)	2,630
	Fiduciary assets	—			—			10,815			—			10,815
	Intercompany receivables	321			2,696			9,419			(12,436		)	—
	Other current assets	1			205			669			(164		)	711
	Total Current Assets	322			3,528			25,138			(14,233		)	14,755
	Goodwill	—			—			9,026			—			9,026
	Intangible assets, net	—			—			2,612			—			2,612
	Fixed assets, net	—			—			760			—			760
	Investments	—			79			64			—			143
	Intercompany receivables	7,408			2,162			2,211			(11,781		)	—
	Other non-current assets	169			498			1,550			(686		)	1,531
	Investment in subsidiary	5,752			16,469			—			(22,221		)	—
	TOTAL ASSETS	$	13,651		$	22,736		$	41,361		$	(48,921	)	$	28,827
	LIABILITIES AND EQUITY
	Fiduciary liabilities	$	—		$	—		$	10,815		$	—		$	10,815
	Short-term debt and current portion of long-term debt	—			649			11			—			660
	Accounts payable and accrued liabilities	1,683			34			1,444			(1,633		)	1,528
	Intercompany payables	8			9,258			3,170			(12,436		)	—
	Other current liabilities	72			47			898			(164		)	853
	Total Current Liabilities	1,763			9,988			16,338			(14,233		)	13,856
	Long-term debt	2,568			1,917			355			—			4,840
	Pension, other post-retirement and other post-employment liabilities	—			854			583			—			1,437
	Intercompany payables	2,100			7,277			2,404			(11,781		)	—
	Other non-current liabilities	5			108			1,995			(686		)	1,422
	TOTAL LIABILITIES	6,436			20,144			21,675			(26,700		)	21,555
	TOTAL AON SHAREHOLDERS' EQUITY	7,215			2,592			19,629			(22,221		)	7,215
	Noncontrolling interests	—			—			57			—			57
	TOTAL EQUITY	7,215			2,592			19,686			(22,221		)	7,272
	TOTAL LIABILITIES AND EQUITY	$	13,651		$	22,736		$	41,361		$	(48,921	)	$	28,827
	Condensed Consolidating Statement of Financial Position
		As of December 31, 2013
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	ASSETS
	Cash and cash equivalents	$	—		$	247		$	1,246		$	(1,016	)	$	477
	Short-term investments	—			163			360			—			523
	Receivables, net	—			4			2,892			—			2,896
	Fiduciary assets	—			—			11,871			—			11,871
	Intercompany receivables	186			3,503			5,452			(9,141		)	—
	Other current assets	—			69			513			(19		)	563
	Total Current Assets	186			3,986			22,334			(10,176		)	16,330
	Goodwill	—			—			8,997			—			8,997
	Intangible assets, net	—			—			2,578			—			2,578
	Fixed assets, net	—			—			791			—			791
	Investments	—			57			75			—			132
	Intercompany receivables	7,166			2,178			2,201			(11,545		)	—
	Other non-current assets	146			560			1,421			(704		)	1,423
	Investment in subsidiary	4,607			11,694			—			(16,301		)	—
	TOTAL ASSETS	$	12,105		$	18,475		$	38,397		$	(38,726	)	$	30,251
	LIABILITIES AND EQUITY
	Fiduciary liabilities	$	—		$	—		$	11,871		$	—		$	11,871
	Short-term debt and current portion of long-term debt	—			—			707			(4		)	703
	Accounts payable and accrued liabilities	1,036			62			1,849			(1,016		)	1,931
	Intercompany payables	15			5,449			3,677			(9,141		)	—
Other current liabilities	12			47			866			(19		)	906
Total Current Liabilities	1,063			5,558			18,970			(10,180		)	15,411
Long-term debt	792			2,512			378			4			3,686
Pension, other post-retirement and other post-employment liabilities	—			925			682			—			1,607
Intercompany payables	2,100			7,267			2,178			(11,545		)	—
Other non-current liabilities	5			159			1,892			(704		)	1,352
TOTAL LIABILITIES	3,960			16,421			24,100			(22,425		)	22,056
TOTAL AON SHAREHOLDERS' EQUITY	8,145			2,054			14,247			(16,301		)	8,145
Noncontrolling interests	—			—			50			—			50
TOTAL EQUITY	8,145			2,054			14,297			(16,301		)	8,195
TOTAL LIABILITIES AND EQUITY	$	12,105		$	18,475		$	38,397		$	(38,726	)	$	30,251
Condensed Consolidating Statements of Cash Flows	'
	Condensed Consolidating Statement of Cash Flows
		Nine months ended September 30, 2014
		Aon			Aon			Other			Consolidating
								Non-Guarantor
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	CASH FLOWS FROM OPERATING ACTIVITIES
	CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	$	309		$	(348	)	$	922		$	—		$	883
	CASH FLOWS FROM INVESTING ACTIVITIES
	Sales of long-term investments	—			39			12			—			51
	Purchase of long-term investments	—			(19		)	—			—			(19		)
	Net sales of short-term investments - non-fiduciary	—			103			198			—			301
	Acquisition of businesses, net of cash acquired	—			—			(464		)	—			(464		)
	Proceeds from sale of businesses	—			—			48			—			48
	Capital expenditures	—			—			(179		)	—			(179		)
	CASH PROVIDED BY (USED FOR) INVESTING ACTIVITIES	—			123			(385		)	—			(262		)
	CASH FLOWS FROM FINANCING ACTIVITIES
	Share repurchase	(1,750		)	—			—			—			(1,750		)
	Advances (to) from affiliates	(253		)	496			371			(614		)	—
	Issuance of shares for employee benefit plans	58			—			—			—			58
	Issuance of debt	2,714			1,541			—			—			4,255
	Repayment of debt	(877		)	(1,491		)	(705		)	—			(3,073		)
	Cash dividends to shareholders	(201		)	—			—			—			(201		)
	Purchase of shares from noncontrolling interests	—			—			1			—			1
	Dividends paid to noncontrolling interests	—			—			(18		)	—			(18		)
	Proceeds from sale-leaseback	—			—			25			—			25
	CASH (USED FOR) PROVIDED BY FINANCING ACTIVITIES	(309		)	546			(326		)	(614		)	(703		)
	EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	—			—			(13		)	—			(13		)
	NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	—			321			198			(614		)	(95		)
	CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	—			247			1,246			(1,016		)	477
	CASH AND CASH EQUIVALENTS AT END OF PERIOD	$	—		$	568		$	1,444		$	(1,630	)	$	382
	Condensed Consolidating Statement of Cash Flows
		Nine months ended September 30, 2013
								Other
		Aon			Aon			Non-Guarantor			Consolidating
	(millions)	plc			Corporation			Subsidiaries			Adjustments			Consolidated
	CASH FLOWS FROM OPERATING ACTIVITIES
	CASH (USED FOR) PROVIDED BY OPERATING ACTIVITIES	$	(14	)	$	(195	)	$	1,193		$	—		$	984
	CASH FLOWS FROM INVESTING ACTIVITIES
	Sales of long-term investments	—			8			73			—			81
	Purchase of long-term investments	—			(13		)	—			—			(13		)
	Net sales of short-term investments - non-fiduciary	—			(35		)	22			—			(13		)
	Acquisition of businesses, net of cash acquired	—			—			(26		)	—			(26		)
	Proceeds from sale of businesses	—			—			6			—			6
	Capital expenditures	—			—			(174		)	—			(174		)
	CASH USED FOR INVESTING ACTIVITIES	—			(40		)	(99		)	—			(139		)
	CASH FLOWS FROM FINANCING ACTIVITIES
	Share repurchase	(1,025		)	—			—			—			(1,025		)
	Advances from (to) affiliates	405			610			(1,014		)	(1		)	—
	Issuance of shares for employee benefit plans	84			—			—			—			84
	Issuance of debt	1,145			2,894			231			—			4,270
	Repayment of debt	(449		)	(3,177		)	(244		)	—			(3,870		)
	Cash dividends to shareholders	(159		)	—			—			—			(159		)
	Purchase of shares from noncontrolling interests	—			—			(6		)	—			(6		)
	Dividends paid to noncontrolling interests	—			—			(13		)	—			(13		)
	CASH PROVIDED BY (USED FOR)	1			327			(1,046		)	(1		)	(719		)
	FINANCING ACTIVITIES
	EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	—			—			(48		)	—			(48		)
	NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(13		)	92			—			(1		)	78
	CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	131			199			—			(39		)	291
	CASH AND CASH EQUIVALENTS AT END OF PERIOD	$	118		$	291		$	—		$	(40	)	$	369

Cash_and_Cash_Equivalents_Deta

Cash and Cash Equivalents (Details)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2013
	USD ($)	GBP (£)	USD ($)	GBP (£)
Cash, Cash Equivalents, and Short-term Investments [Abstract]	'	'	'	'
Short-term investment, minimum maturity period	'3 months	'3 months	'	'
Short-term investment, maximum maturity period	'1 year	'1 year	'	'
Cash and Cash Equivalents and Short-Term Investments	$599	'	$1,000	'
Restricted Cash and Investments, Current	144	'	214	'
Operating funds in U.K.	66	40.5	126	77
Cash and cash equivalents, restricted	$78	'	$88	'

Schedule_of_Other_Income_Detai

Schedule of Other Income (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Other (Expense) Income	'	'	'	'
Equity earnings	$4	$6	$10	$12
Gain on investments	4	37	2	36
Foreign currency remeasurement gain (loss)	7	-4	11	15
Derivative (loss) gain	-6	1	-19	-8
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	25	0	25	0
Other	1	-1	5	-1
Other Income	$35	$39	$34	$54

Other_Financial_Data_Schedule_

Other Financial Data Schedule of Allowance for Doubtful Accounts (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]	'	'	'	'
Balance at beginning of period	$88	$114	$90	$118
Provision charged to operations	1	-5	9	6
Accounts written off, net of recoveries	-14	-8	-23	-26
Effect of exchange rate changes and other	4	-2	3	1
Balance at end of period	$79	$99	$79	$99

Other_Financial_Data_Schedule_1

Other Financial Data Schedule of Other Current Assets (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Financial Data [Abstract]	'	'
Taxes receivable	$258	$111
Prepaid expenses	238	229
Deferred project costs	102	98
Deferred tax assets	81	93
Other	32	32
Other Assets, Current	$711	$563

Other_Financial_Data_Schedule_2

Other Financial Data Schedule of Non-current Assets (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Other Financial Data [Abstract]	'		'
Prepaid pension	$750	[1]	$567	[1]
Deferred project costs	256		273
Deferred tax assets	176		193
Taxes receivable	98		108
Other	251		282
Other Assets, Noncurrent	$1,531		$1,423
[1]	Increase in prepaid pensions is primarily due to cash funding of the U.K. pension plans.

Other_Financial_Data_Schedule_3

Other Financial Data Schedule of Other Current Liabilities (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Financial Data [Abstract]	'	'
Deferred revenue	$440	$475
Taxes payable	96	136
Deferred tax liabilities	36	48
Other	281	247
Other Liabilities, Current	$853	$906

Other_Financial_Data_Schedule_4

Other Financial Data Schedule of Other Non-current Liabilities (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Financial Data [Abstract]	'	'
Deferred tax liabilities	$535	$420
Taxes payable	202	184
Leases	191	204
Deferred revenue	170	134
Compensation and benefits	56	105
Other	268	305
Other Liabilities, Noncurrent	$1,422	$1,352

Acquisitions_and_Dispositions_1

Acquisitions and Dispositions - Acquisitions (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
	business	business	business	business
Intangible assets:	'	'	'	'	'
Goodwill	$9,026	'	$9,026	'	$8,997
Business Acquisition 1 [Member]	'	'	'	'	'
Business Acquisition	'	'	'	'	'
Consideration	446	26	446	26	'
Intangible assets:	'	'	'	'	'
Goodwill	261	26	261	26	'
Other intangible assets	310	8	310	8	'
Total	571	34	571	34	'
Risk Solutions [Member]	'	'	'	'	'
Business Acquisition	'	'	'	'	'
Number of business acquired under business combination	4	1	7	5	'
Intangible assets:	'	'	'	'	'
Goodwill	6,057	'	6,057	'	6,020
HR Solutions [Member]	'	'	'	'	'
Business Acquisition	'	'	'	'	'
Number of business acquired under business combination	1	1	2	2	'
Intangible assets:	'	'	'	'	'
Goodwill	$2,969	'	$2,969	'	$2,977

Acquisitions_and_Dispositions_2

Acquisitions and Dispositions - Dispositions (Details) (Risk Solutions [Member], USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
	business	business	business	business
Risk Solutions [Member]	'	'	'	'
Dispositions	'	'	'	'
Number of dispositions	1	1	2	5
Gain (loss) recognized on sale	$25	$0.20	$25	$0.20

Goodwill_and_Other_Intangible_2

Goodwill and Other Intangible Assets (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Changes in the net carrying amount of goodwill by operating segment (in millions)	'
Beginning balance	$8,997
Goodwill related to current year acquisitions	261
Goodwill related to disposals	-14
Goodwill related to prior year acquisitions	-1
Transfer	0
Foreign currency translation	-217
Ending balance	9,026
Risk Solutions [Member]	'
Changes in the net carrying amount of goodwill by operating segment (in millions)	'
Beginning balance	6,020
Goodwill related to current year acquisitions	256
Goodwill related to disposals	-14
Goodwill related to prior year acquisitions	-1
Transfer	-2
Foreign currency translation	-202
Ending balance	6,057
HR Solutions [Member]	'
Changes in the net carrying amount of goodwill by operating segment (in millions)	'
Beginning balance	2,977
Goodwill related to current year acquisitions	5
Goodwill related to disposals	0
Goodwill related to prior year acquisitions	0
Transfer	2
Foreign currency translation	-15
Ending balance	$2,969

Goodwill_and_Other_Intangible_3

Goodwill and Other Intangible Assets (Details 2) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Intangible assets with indefinite lives	'	'	'	'	'
Tradenames	$1,019	'	$1,019	'	$1,019
Intangible assets with finite lives	'	'	'	'	'
Intangible assets with finite lives, Gross Carrying Amount	4,579	'	4,579	'	4,323
Intangible assets with finite lives, Accumulated Amortization	1,967	'	1,967	'	1,745
Intangible assets, Net Carrying Amount	2,612	'	2,612	'	2,578
Amortization expense on intangible assets	90	98	263	296	'
Estimated amortization for intangible assets	'	'	'	'	'
Remainder of 2014	89	'	89	'	'
2015	320	'	320	'	'
2016	276	'	276	'	'
2017	231	'	231	'	'
2018	172	'	172	'	'
Thereafter	505	'	505	'	'
Estimated future amortization for intangible assets	1,593	'	1,593	'	'
Risk Solutions [Member]	'	'	'	'	'
Estimated amortization for intangible assets	'	'	'	'	'
Remainder of 2014	29	'	29	'	'
2015	109	'	109	'	'
2016	100	'	100	'	'
2017	91	'	91	'	'
2018	79	'	79	'	'
Thereafter	253	'	253	'	'
Estimated future amortization for intangible assets	661	'	661	'	'
HR Solutions [Member]	'	'	'	'	'
Estimated amortization for intangible assets	'	'	'	'	'
Remainder of 2014	60	'	60	'	'
2015	211	'	211	'	'
2016	176	'	176	'	'
2017	140	'	140	'	'
2018	93	'	93	'	'
Thereafter	252	'	252	'	'
Estimated future amortization for intangible assets	932	'	932	'	'
Customer related and contract based [Member]	'	'	'	'	'
Intangible assets with finite lives	'	'	'	'	'
Intangible assets with finite lives, Gross Carrying Amount	2,972	'	2,972	'	2,720
Intangible assets with finite lives, Accumulated Amortization	1,520	'	1,520	'	1,310
Intangible assets, Net Carrying Amount	1,452	'	1,452	'	1,410
Marketing, technology and other [Member]	'	'	'	'	'
Intangible assets with finite lives	'	'	'	'	'
Intangible assets with finite lives, Gross Carrying Amount	588	'	588	'	584
Intangible assets with finite lives, Accumulated Amortization	447	'	447	'	435
Intangible assets, Net Carrying Amount	$141	'	$141	'	$149

Restructuring_Details

Restructuring (Details) (USD $)	9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
			Aon Hewitt Restructuring Plan [Member]	Aon Hewitt Restructuring Plan [Member]	Aon Hewitt Restructuring Plan [Member]	Aon Hewitt Restructuring Plan [Member]	Aon Hewitt Restructuring Plan [Member]	Aon Hewitt Restructuring Plan [Member]
					HR Solutions [Member]	HR Solutions [Member]	Risk Solutions [Member]	Risk Solutions [Member]
Restructuring Cost and Reserve [Line Items]	'	'	'	'	'	'	'	'
Restructuring charges	'	'	$30	$109	$6	$57	$24	$52
Restructuring reserve	90	166	'	'	'	'	'	'
Cash payments	70	'	'	'	'	'	'	'
Restructuring reserve reduction due to foreign currency translation	$6	'	'	'	'	'	'	'

Investments_Details

Investments (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Interest-bearing Assets	'		'		'	'
Cash and cash equivalents	$382		$477		$369	$291
Short-term investments	217		523		'	'
Fiduciary assets	3,877	[1]	3,778	[1]	'	'
Investments	143		132		'	'
Total interest-bearing assets	4,619		4,910		'	'
Investments:	'		'		'	'
Equity method investments	122		113		'	'
Other investments	13		10		'	'
Fixed-maturity securities	8		9		'	'
Investments	$143		$132		'	'
[1]	Fiduciary assets include funds held on behalf of clients but does not include fiduciary receivables.

Debt_Details

Debt (Details)

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

Jun. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Aug. 12, 2014

20-May-14

Jul. 01, 2014

Jul. 01, 2014

Jun. 30, 2014

20-May-14

7-May-14

Jul. 01, 2014

Sep. 30, 2014

EUR (€)

Commercial paper [Member]

Commercial paper [Member]

Commercial paper [Member]

3.50% debt securities due September 2015 [Member]

3.50% notes due 2024 [Member]

3.50% notes due 2024 [Member]

Debt Securities 6.25 Percent, Due 2014 [Member]

Debt Securities 6.25 Percent, Due 2014 [Member]

Debt Securities 6.25 Percent, Due 2014 [Member]

4.60% notes due 2044 [Member]

2.875% notes due 2026 [Member]

Debt Securities 6.25 Percent, Due 2014 [Member]

Short-term debt and current portion of long-term debt [Member]

USD ($)

USD ($)

USD ($)

Notes Payable, Other Payables [Member]

Notes Payable, Other Payables [Member]

Notes Payable, Other Payables [Member]

EUR (€)

Notes Payable, Other Payables [Member]

Notes Payable, Other Payables [Member]

Notes Payable, Other Payables [Member]

Notes Payable, Other Payables [Member]

EUR (€)

3.50% debt securities due September 2015 [Member]

USD ($)

USD ($)

EUR (€)

USD ($)

EUR (€)

USD ($)

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total debt

'

$50,000,000

$50,000,000

$0

'

'

'

'

'

'

'

'

'

'

Weighted average commercial paper outstanding

'

360,000,000

338,000,000

'

'

'

'

'

'

'

'

'

'

'

Weighted-average interest rates (as a percent)

'

0.31%

0.34%

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Face Amount

'

'

'

'

'

350,000,000

250,000,000

'

'

500,000,000

550,000,000

500,000,000

'

600,000,000

Debt interest rate percentage

'

'

'

'

3.50%

3.50%

3.50%

'

6.25%

6.25%

4.60%

2.88%

'

'

Repayments of Debt

'

'

'

'

'

'

'

531,000,000

'

'

'

'

'

'

Payments for Deposits Applied to Debt Retirements

531,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Repayment of debt

'

'

'

'

'

'

'

'

'

'

'

'

€ 500,000,000

'

Income_Taxes_Income_Taxes_Deta

Income Taxes Income Taxes (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Effective income tax rate	19.10%	25.10%	18.50%	25.90%

Shareholders_Equity_Details

Shareholders' Equity (Details) (USD $)	1 Months Ended	3 Months Ended				9 Months Ended				30 Months Ended
	Apr. 30, 2012	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014
Common Stock Programs	'	'		'		'		'		'
Total cost of shares purchased	'	'		'		$1,750,000,000		'		'
Weighted average shares outstanding	'	'		'		'		'		'
Shares for basic earnings per share (in shares)	'	292,300,000	[1]	309,500,000	[1]	298,100,000	[1]	313,200,000	[1]	'
Common stock equivalents (in shares)	'	3,800,000		3,400,000		3,500,000		3,500,000		'
Shares for diluted earnings per share (in shares)	'	296,100,000		312,900,000		301,600,000		316,700,000		'
Number of participating securities (in shares)	'	2,900,000		3,800,000		3,100,000		4,000,000		'
Number of shares excluded from the calculation of diluted earnings per share	'	0		0		0		0		'
2012 - Share Repurchase Program [Member]	'	'		'		'		'		'
Common Stock Programs	'	'		'		'		'		'
Share repurchase authorization limit	5,000,000,000	'		'		'		'		'
Shares purchased (in shares)	'	5,800,000		7,300,000		20,400,000		15,800,000		56,700,000
Average price per share of stock repurchased	'	$86.07		$68.33		$85.73		$64.79		'
Total cost of shares purchased	'	500,000,000		500,000,000		1,800,000,000		1,000,000,000		3,900,000,000
Share repurchase, remaining authorization limit	'	'		'		$1,100,000,000		'		'
[1]	Includes 2.9 million and 3.8 million of participating securities for the three months ended SeptemberB 30, 2014 and 2013, respectively, and 3.1 million and 4.0 million of participating securities for the nine months ended SeptemberB 30, 2014 and 2013, respectively.

Shareholders_Equity_Schedule_o

Shareholders' Equity Schedule of Net Income from Participating Securities (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]	'	'	'	'
Net income from participating securities	$2	$3	$7	$8

Shareholders_Equity_Details_2

Shareholders' Equity (Details 2) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Beginning balance	($2,374)
Other comprehensive (loss) income before reclassifications, net	-224
Amounts reclassified from accumulated other comprehensive loss:	'
Amounts reclassified from accumulated other comprehensive loss	111
Tax benefit	-31
Amounts reclassified from accumulated other comprehensive loss, net	80
Net current period other comprehensive (loss) income	-144
Ending balance	-2,518
Change in Fair Value of Investments [Member]	'
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Beginning balance	1	[1]
Other comprehensive (loss) income before reclassifications, net	-1	[1]
Amounts reclassified from accumulated other comprehensive loss:	'
Amounts reclassified from accumulated other comprehensive loss	0	[1]
Tax benefit	0	[1]
Amounts reclassified from accumulated other comprehensive loss, net	0	[1]
Net current period other comprehensive (loss) income	-1	[1]
Ending balance	0	[1]
Change in Fair Value of Derivatives [Member]	'
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Beginning balance	-22	[1]
Other comprehensive (loss) income before reclassifications, net	1	[1]
Amounts reclassified from accumulated other comprehensive loss:	'
Amounts reclassified from accumulated other comprehensive loss	17	[1]
Tax benefit	-5	[1]
Amounts reclassified from accumulated other comprehensive loss, net	12	[1]
Net current period other comprehensive (loss) income	13	[1]
Ending balance	-9	[1]
Foreign Currency Translation Adjustments [Member]	'
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Beginning balance	169
Other comprehensive (loss) income before reclassifications, net	-226
Amounts reclassified from accumulated other comprehensive loss:	'
Amounts reclassified from accumulated other comprehensive loss	0
Tax benefit	0
Amounts reclassified from accumulated other comprehensive loss, net	0
Net current period other comprehensive (loss) income	-226
Ending balance	-57
Post-Retirement Benefit Obligation [Member]	'
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Beginning balance	-2,522	[2]
Other comprehensive (loss) income before reclassifications, net	2	[2]
Amounts reclassified from accumulated other comprehensive loss:	'
Amounts reclassified from accumulated other comprehensive loss	94	[2]
Tax benefit	-26	[2]
Amounts reclassified from accumulated other comprehensive loss, net	68	[2]
Net current period other comprehensive (loss) income	70	[2]
Ending balance	($2,452)	[2]
[1]	Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Other income.
[2]	Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Compensation and benefits.

Employee_Benefits_Details

Employee Benefits (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
U.K. [Member]	'	'	'	'
Defined Benefit Plan Disclosure	'	'	'	'
Service cost	$0	$0	$0	$0
Interest cost	58	52	174	156
Expected return on plan assets	-82	-74	-247	-223
Amortization of net actuarial loss	13	12	40	36
Net periodic (benefit) cost	'	'	-33	-31
Curtailment loss (gain) and other	'	'	0	0
Total net periodic (benefit) cost	-11	-10	-33	-31
Estimate of contributions to defined benefit pension plans for the current fiscal year	183	'	183	'
Contributions made to defined benefit pension plans	24	54	145	241
U.S. [Member]	'	'	'	'
Defined Benefit Plan Disclosure	'	'	'	'
Service cost	0	0	0	0
Interest cost	32	28	96	84
Expected return on plan assets	-39	-34	-117	-103
Amortization of net actuarial loss	11	13	32	39
Net periodic (benefit) cost	'	'	11	20
Curtailment loss (gain) and other	'	'	1	0
Total net periodic (benefit) cost	4	7	12	20
Estimate of contributions to defined benefit pension plans for the current fiscal year	173	'	173	'
Contributions made to defined benefit pension plans	39	54	112	122
Other [Member]	'	'	'	'
Defined Benefit Plan Disclosure	'	'	'	'
Service cost	0	5	0	14
Interest cost	12	11	36	33
Expected return on plan assets	-15	-15	-45	-44
Amortization of net actuarial loss	2	6	6	19
Net periodic (benefit) cost	'	'	-3	22
Curtailment loss (gain) and other	'	'	-3	0
Total net periodic (benefit) cost	-1	7	-6	22
Estimate of contributions to defined benefit pension plans for the current fiscal year	29	'	29	'
Contributions made to defined benefit pension plans	$7	$5	$23	$49

ShareBased_Compensation_Plans_1

Share-Based Compensation Plans Share-based compensation expenses recognized (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total share-based compensation expense	$72	$70	$247	$207
Restricted share units (RSUs) [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total share-based compensation expense	41	40	144	135
Performance share awards (bPSAsb) [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total share-based compensation expense	29	28	96	66
Share options [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total share-based compensation expense	0	0	0	1
Employee share purchase plans [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total share-based compensation expense	$2	$2	$7	$5

ShareBased_Compensation_Plans_2

Share-Based Compensation Plans Restricted share unit activity (Details) (Restricted share units (RSUs) [Member], USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Restricted share units (RSUs) [Member]	'		'
Non-vested share awards (in shares)	'		'
Non-vested at beginning of period	9,759		10,432
Granted	2,675		3,598
Vested	-3,561		-3,618
Forfeited	-385		-308
Non-vested at end of period	8,488		10,104
Weighted Average Fair value (in dollars per share)	'		'
Non-vested at beginning of period	$51	[1]	$44	[1]
Granted	$84	[1]	$62	[1]
Vested	$49	[1]	$44	[1]
Forfeited	$56	[1]	$47	[1]
Non-vested at end of period	$63	[1]	$51	[1]
[1]	Represents per share weighted average fair value of award at date of grant

ShareBased_Compensation_Plans_3

Share-Based Compensation Plans Performance Share Awards Narrative (Details) (Performance Shares [Member])	9 Months Ended
	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Vesting conditions period	'3 years
Minimum [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares issued, percent	0.00%
Maximum [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares issued, percent	200.00%

ShareBased_Compensation_Plans_4

Share-Based Compensation Plans Schedule of Performance-based plans (Details) (Performance Shares [Member], USD $)	9 Months Ended		12 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013		Dec. 31, 2012
Performance Shares [Member]	'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'
Target PSAs granted	816		1,135		1,369
Fair value	$81	[1]	$58	[1]	$47	[1]
Number of shares that would be issued based on current performance levels	804		2,211		2,656
Unamortized expense, based on current performance levels	$52		$57		$11
[1]	Represents per share weighted average fair value of award at date of grant.

ShareBased_Compensation_Plans_5

Share-Based Compensation Plans Share options activity (Details) (Share options [Member], USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Share options [Member]	'	'
Share Options (in shares)	'	'
Beginning outstanding	3,462	5,611
Granted	0	0
Exercised	-953	-1,694
Forfeited and expired	-6	-29
Outstanding at end of period	2,503	3,888
Exercisable at end of period	2,464	3,681
Weighted-Average Exercise Price (in dollars per share)	'	'
Beginning outstanding	$32	$32
Granted	$0	$0
Exercised	$32	$32
Forfeited and expired	$37	$34
Outstanding at end of period	$32	$32
Exercisable at end of period	$32	$32

ShareBased_Compensation_Plans_6

Share-Based Compensation Plans Stock Option Narrative (Details) (USD $)	9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Closing share price (in dollars per share)	87.67	'
Aggregate intrinsic value of options outstanding	138	'
Aggregate intrinsic value of exercisable options outstanding	137	'
Unamortized deferred compensation expense	395	'
Remaining weighted-average amortization period	'2 years 1 month 6 days	'
Share options [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Weighted average remaining contractual life	'1 year 8 months 12 days	'2 years 2 months 24 days

ShareBased_Compensation_Plans_7

Share-Based Compensation Plans Other information related to the company's share options (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'	'
Aggregate intrinsic value of stock options exercised	$6	$14	$51	$53
Cash received from the exercise of stock options	3	14	30	55
Tax benefit realized from the exercise of stock options	$2	$3	$14	$10

Derivatives_and_Hedging_Foreig

Derivatives and Hedging Foreign Exchange Risk Management Narrative (Details)	9 Months Ended
	Sep. 30, 2014
Not Designated as Hedging Instrument [Member]	'
Derivative [Line Items]	'
Foreign currency exposures, maximum hedging period	'1 year
Cash Flow Hedging [Member]	'
Derivative [Line Items]	'
Foreign currency exposures, maximum average hedging period	'2 years
Foreign currency exposures, maximum hedging period	'5 years
Net Investment Hedging [Member]	'
Derivative [Line Items]	'
Foreign currency exposures, maximum hedging period	'2 years

Derivatives_and_Hedging_Intere

Derivatives and Hedging Interest Rate Management Risk Narrative (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative [Line Items]	'	'	'	'
Estimated pretax losses currently included within Accumulated Other Comprehensive Loss that will be reclassified to earnings in next twelve months	$3	'	$3	'
Amount of Gain (Loss) Recognized in Income on Derivative	-6	1	-19	-8
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]	'	'	'	'
Derivative [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivative	($11)	$3	($13)	($15)
Cash Flow Hedging [Member]	'	'	'	'
Derivative [Line Items]	'	'	'	'
Interest rate fluctuations, maximum hedging period	'	'	'2 years	'

Derivatives_and_Hedging_Notion

Derivatives and Hedging Notional and fair values of derivative instruments (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Derivatives, Fair Value	'		'
Notional Amount	$1,290		$1,577
Derivative Assets	55	[1]	80	[1]
Derivative Liabilities	65	[2]	93	[2]
Gross Amounts Offset in the Statement of Financial Position	-15		-30
Net Amounts of Assets Presented in the Statement of Financial Position	40	[3]	50	[3]
Gross Amounts Offset in the Statement of Financial Position	-15		-30
Net Amounts of Liabilities Presented in the Statement of Financial Position	50	[4]	63	[4]
Other Current Assets [Member]	'		'
Derivatives, Fair Value	'		'
Derivative Assets	25		46
Net Amounts of Assets Presented in the Statement of Financial Position	13		18
Other Noncurrent Assets [Member]	'		'
Derivatives, Fair Value	'		'
Derivative Assets	30		34
Net Amounts of Assets Presented in the Statement of Financial Position	27		32
Other Current Liabilities [Member]	'		'
Derivatives, Fair Value	'		'
Derivative Liabilities	17		51
Net Amounts of Liabilities Presented in the Statement of Financial Position	5		23
Other Noncurrent Liabilities [Member]	'		'
Derivatives, Fair Value	'		'
Derivative Liabilities	48		42
Net Amounts of Liabilities Presented in the Statement of Financial Position	45		40
Derivatives accounted for as hedges [Member]	'		'
Derivatives, Fair Value	'		'
Notional Amount	1,106		1,362
Derivative Assets	55	[1]	80	[1]
Derivative Liabilities	65	[2]	93	[2]
Gross Amounts Offset in the Statement of Financial Position	-15		-30
Net Amounts of Assets Presented in the Statement of Financial Position	40	[3]	50	[3]
Gross Amounts Offset in the Statement of Financial Position	-15		-30
Net Amounts of Liabilities Presented in the Statement of Financial Position	50	[4]	63	[4]
Derivatives accounted for as hedges [Member] | Interest rate contracts [Member]	'		'
Derivatives, Fair Value	'		'
Notional Amount	0		171
Derivative Assets	0	[1]	9	[1]
Derivative Liabilities	0	[2]	0	[2]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Assets Presented in the Statement of Financial Position	0	[3]	9	[3]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Liabilities Presented in the Statement of Financial Position	0	[4]	0	[4]
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member]	'		'
Derivatives, Fair Value	'		'
Notional Amount	1,106		1,191
Derivative Assets	55	[1]	71	[1]
Derivative Liabilities	65	[2]	93	[2]
Gross Amounts Offset in the Statement of Financial Position	-15		-30
Net Amounts of Assets Presented in the Statement of Financial Position	40	[3]	41	[3]
Gross Amounts Offset in the Statement of Financial Position	-15		-30
Net Amounts of Liabilities Presented in the Statement of Financial Position	50	[4]	63	[4]
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]	'		'
Derivatives, Fair Value	'		'
Notional Amount	184		215
Derivative Assets	0	[1]	0	[1]
Derivative Liabilities	0	[2]	0	[2]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Assets Presented in the Statement of Financial Position	0	[3]	0	[3]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Liabilities Presented in the Statement of Financial Position	$0	[4]	$0	[4]
[1]	Included within Other current assets ($25 million and $46 millionB at September 30, 2014 and DecemberB 31, 2013, respectively) or Other non-current assets ($30 million and $34 millionB at September 30, 2014 and DecemberB 31, 2013, respectively).
[2]	Included within Other current liabilities ($17 million and $51 millionB at September 30, 2014 and DecemberB 31, 2013, respectively) or Other non-current liabilities ($48 million and $42 millionB at September 30, 2014 and DecemberB 31, 2013, respectively).
[3]	Included within Other current assets ($13 million and $18 millionB at September 30, 2014 and DecemberB 31, 2013, respectively) or Other non-current assets ($27 million and $32 millionB at September 30, 2014 and DecemberB 31, 2013, respectively).
[4]	Included within Other current liabilities ($5 million and $23 millionB at September 30, 2014 and DecemberB 31, 2013, respectively) or Other non-current liabilities ($45 million and $40 millionB at September 30, 2014 and DecemberB 31, 2013, respectively).

Derivatives_and_Hedging_Deriva

Derivatives and Hedging Derivatives gains (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Derivative Instruments, Gain (Loss)	'		'		'		'
Amount of Gain (Loss) Recognized in Income on Derivative	($6)		$1		($19)		($8)
Derivatives accounted for as hedges [Member] | Cash Flow Hedging [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	-3		0		4		-28
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	4		-10		-16		-8
Derivatives accounted for as hedges [Member] | Cash Flow Hedging [Member] | Compensation and Benefits [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	-2		-3		14		-17
Derivatives accounted for as hedges [Member] | Cash Flow Hedging [Member] | Other Income [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	2		3		-9		-11
Derivatives accounted for as hedges [Member] | Cash Flow Hedging [Member] | Sponsorship Fees [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	-3		'		-1		'
Derivatives accounted for as hedges [Member] | Interest rate contracts [Member] | Cash Flow Hedging [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	0	[1]	0	[1]	0	[1]	0	[1]
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	[2]	0	[2]	-1	[2]	-1	[2]
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member] | Cash Flow Hedging [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) recognized in Accumulated Other Comprehensive Loss:	-3	[3]	0	[3]	4	[3]	-28	[3]
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	4	[4]	-10	[4]	-15	[4]	-7	[4]
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member] | Cash Flow Hedging [Member] | Compensation and Benefits [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	-1		-5		-4		-9
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member] | Cash Flow Hedging [Member] | Other Income [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	5		-5		-6		3
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member] | Cash Flow Hedging [Member] | Sponsorship Fees [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	3		'		3		-1
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	-3		'		-8		'
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member] | Fair value hedges	'		'		'		'
Derivative Instruments, Gain (Loss)	'		'		'		'
Amount of Gain (Loss) Recognized in Income on Derivative	-9	[5],[6]	-7	[5],[6]	-9	[5],[6]	-8	[5],[6]
Amount of Gain (Loss) Recognized in Income on Related Hedged Item	$9	[6]	$7	[6]	$9	[5],[6]	$8	[5],[6]
[1]	Location of future reclassification from Accumulated Other Comprehensive Loss will be included within Interest expense
[2]	Included within Interest expense
[3]	Location of future reclassification from Accumulated Other Comprehensive Loss will be included within Compensation and benefits ($2 million and $3 million loss for the three months ended September 30, 2014 and 2013, respectively, and $14 million gain and $17 million loss for the nine months ended September 30, 2014 and 2013, respectively), Other income ($2 million and $3 millionB gain for the three months ended September 30, 2014 and 2013, respectively, and $9 million and $11 million loss for the nine months ended September 30, 2014 and 2013, respectively), and Other general expenses ($3 million and $1 million loss for the three and nine months ended September 30, 2014, respectively).
[4]	Included within Compensation and benefits ($1 million and $5 millionB loss for the three months ended September 30, 2014 and 2013, respectively, and $4 million and $9 million loss for the nine months ended September 30, 2014 and 2013, respectively), Other income ($5 million gain and $5 millionB loss for the three months ended September 30, 2014 and 2013, respectively, and $6 million loss and $3 million gain for the nine months ended September 30, 2014 and 2013, respectively), Interest expenses ($3 million and $8 million loss for the three and nine months ended September 30, 2014, respectively), and Other general expenses ($3 million gain for the three months ended September 30, 2014, and $3 million gain and $1 million loss for the nine months ended September 30, 2014 and 2013, respectively).
[5]	Relates to fixed rate debt.
[6]	Included in Interest expense.

Fair_Value_Measurements_and_Fi2

Fair Value Measurements and Financial Instruments Schedule of assets and liabilities that are measured at fair value on a recurring basis (Details) (USD $)

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Recurring [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Fair Value [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Other Observable Inputs (Level 2) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Money market funds and highly liquid debt securities

Money market funds and highly liquid debt securities

Money market funds [Member]

Money market funds [Member]

Highly liquid debt securities [Member]

Highly liquid debt securities [Member]

Corporate bonds [Member]

Corporate bonds [Member]

Government bonds [Member]

Government bonds [Member]

Equity securities [Member]

Equity securities [Member]

Interest rate contracts [Member]

Interest rate contracts [Member]

Foreign exchange contracts [Member]

Foreign exchange contracts [Member]

Money market funds and highly liquid debt securities

Money market funds and highly liquid debt securities

Corporate bonds [Member]

Corporate bonds [Member]

Government bonds [Member]

Government bonds [Member]

Equity securities [Member]

Equity securities [Member]

Interest rate contracts [Member]

Interest rate contracts [Member]

Foreign exchange contracts [Member]

Foreign exchange contracts [Member]

Money market funds and highly liquid debt securities

Money market funds and highly liquid debt securities

Corporate bonds [Member]

Corporate bonds [Member]

Government bonds [Member]

Government bonds [Member]

Equity securities [Member]

Equity securities [Member]

Interest rate contracts [Member]

Interest rate contracts [Member]

Foreign exchange contracts [Member]

Foreign exchange contracts [Member]

Money market funds and highly liquid debt securities

Money market funds and highly liquid debt securities

Corporate bonds [Member]

Corporate bonds [Member]

Government bonds [Member]

Government bonds [Member]

Equity securities [Member]

Equity securities [Member]

Interest rate contracts [Member]

Interest rate contracts [Member]

Foreign exchange contracts [Member]

Foreign exchange contracts [Member]

Fair Value Disclosures [Abstract]

'

'

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'

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'

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'

'

'

'

'

'

'

'

'

'

Net assets value (in dollar per share)

'

$1

'

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

'

'

'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Realized gain

$6,000,000

'

$6,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrealized gain (loss)

0

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

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Assets:

'

'

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'

'

'

'

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'

'

'

'

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'

'

'

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'

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'

'

'

'

'

'

'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Money market funds and highly liquid debt securities

'

'

'

1,649,000,000

[1]

2,079,000,000

[2]

1,647,000,000

2,054,000,000

2,000,000

25,000,000

'

'

'

'

'

'

'

'

'

'

1,647,000,000

[1]

2,054,000,000

[2]

'

'

'

'

'

'

'

'

'

'

2,000,000

[1]

25,000,000

[2]

'

'

'

'

'

'

'

'

'

'

0

[1]

0

[2]

'

'

'

'

'

'

'

'

'

'

Other investments

'

'

'

'

'

'

'

'

'

1,000,000

2,000,000

7,000,000

7,000,000

11,000,000

13,000,000

'

'

'

'

'

'

0

0

0

0

6,000,000

6,000,000

'

'

'

'

'

'

0

0

7,000,000

7,000,000

5,000,000

7,000,000

'

'

'

'

'

'

1,000,000

2,000,000

0

0

0

0

'

'

'

'

Derivatives

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

9,000,000

55,000,000

71,000,000

'

'

'

'

'

'

'

'

0

0

0

0

'

'

'

'

'

'

'

'

0

9,000,000

55,000,000

71,000,000

'

'

'

'

'

'

'

'

0

0

0

0

Liabilities:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

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'

'

'

'

'

'

Derivatives

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$65,000,000

$93,000,000

'

'

'

'

'

'

'

'

'

'

$0

$0

'

'

'

'

'

'

'

'

'

'

$65,000,000

$93,000,000

'

'

'

'

'

'

'

'

'

'

$0

$0

[1]

Includes $1,647 million of money market funds and $2 million of highly liquid debt securities that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity. See Note 8 "Investments" for additional information regarding the Company's investments.

[2]

Includes $2,054 million of money market funds and $25 million of highly liquid debt securities that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity. See Note 8 "Investments" for additional information regarding the Company's investments.

Fair_Value_Measurements_and_Fi3

Fair Value Measurements and Financial Instruments Schedule of financial instruments where the carrying amounts and fair values differ (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair value of financial instrument	'	'
Carrying value of total debt	$4,840	$3,686
Fair value of total debt	$5,190	$3,894

Commitments_and_Contingencies_

Commitments and Contingencies (Details)

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Apr. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Jun. 15, 2011

Mar. 20, 2012

Mar. 20, 2012

Oct. 15, 2010

Jan. 31, 2014

Sep. 14, 2010

Sep. 30, 2014

Jan. 02, 2014

Dec. 12, 2012

Sep. 30, 2014

Jun. 01, 2007

Jun. 01, 2007

Jun. 01, 2007

Sep. 30, 2014

Dec. 27, 2012

Oct. 27, 2014

USD ($)

USD ($)

Potential Claim for Pension Advisory Services [Member]

Potential Claim for Pension Advisory Services [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Commitments to fund certain limited partnerships or subsidiaries [Member]

Northrop Grumman Corporation [Member]

Opry Mills Mall Limited Partnership [Member]

Philips [Member]

Philips [Member]

Mazeikiu Nafta [Member]

International Road Transport Union [Member]

International Road Transport Union [Member]

International Road Transport Union [Member]

International Road Transport Union [Member]

Versicherung Aktiengesellschaft [Member]

Versicherung Aktiengesellschaft [Member]

Subsequent Event [Member]

USD ($)

GBP (£)

USD ($)

USD ($)

USD ($)

Subsidiaries [Member]

Subsidiaries [Member]

Subsidiaries [Member]

Subsidiaries [Member]

USD ($)

USD ($)

USD ($)

GBP (£)

USD ($)

Litigation Award [Member]

Litigation Award [Member]

Litigation USD Denominated Award [Member]

Litigation Expenses and Interest [Member]

Litigation Award [Member]

Litigation Award [Member]

Mazeikiu Nafta [Member]

Term Credit Agreement [Member]

Five-Year Agreement [Member]

Five-Year Agreement [Member]

Euro Facility Agreement [Member]

USD ($)

CHF

USD ($)

USD ($)

USD ($)

EUR (€)

USD ($)

USD ($)

USD ($)

EUR (€)

Legal, Guarantees and Indemnifications

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Range of Possible Loss, Minimum

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Range of Possible Loss, Maximum

700,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Damages sought

'

'

'

'

'

'

'

'

'

'

'

340,000,000

200,000,000

307,000,000

189,000,000

125,000,000

48,000,000

46,000,000

3,000,000

30,000,000

232,000,000

183,000,000

'

Days of trial

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'11 days

Case settlement amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,000,000

Amount of coverage for damages contended by the insurers

'

'

'

'

'

'

'

'

'

'

'

'

50,000,000

'

'

'

'

'

'

'

'

'

'

Difference amount of damages sought by the client

'

'

'

'

'

'

'

'

'

'

'

'

150,000,000

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Estimate of Possible Loss

'

'

73,000,000

45,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum potential funding under commitments

83,000,000

98,000,000

'

'

16,000,000

16,000,000

34,000,000

450,000,000

'

400,000,000

650,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Term of credit agreement

'

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letters of credit outstanding

97,000,000

71,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitments funded

'

'

'

'

$4,000,000

$18,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
			segment
Segment Reporting Information	'	'	'	'
Number of reportable segments	'	'	2	'
Total revenue	$2,880	$2,794	$8,746	$8,606
Total commissions, fees and other revenue	2,873	2,786	8,727	8,585
Total fiduciary investment income	7	8	19	21
Operating income before income tax	417	364	1,331	1,156
Interest income	3	3	7	6
Interest expense	-65	-53	-188	-153
Other income	35	39	34	54
Income before income taxes	390	353	1,184	1,063
Total operating segments [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Operating income before income tax	456	408	1,454	1,289
Risk Solutions [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total revenue	1,836	1,821	5,778	5,736
Total commissions, fees and other revenue	1,829	1,813	5,759	5,715
Total fiduciary investment income	7	8	19	21
Operating income before income tax	343	333	1,205	1,127
Retail brokerage [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total commissions, fees and other revenue	1,458	1,424	4,619	4,548
Reinsurance brokerage [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total commissions, fees and other revenue	371	389	1,140	1,167
HR Solutions [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total revenue	1,057	981	3,004	2,891
Total commissions, fees and other revenue	1,057	981	3,004	2,891
Total fiduciary investment income	0	0	0	0
Operating income before income tax	113	75	249	162
Consulting services [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total commissions, fees and other revenue	466	406	1,245	1,176
Outsourcing [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total commissions, fees and other revenue	604	587	1,788	1,746
Intrasegment [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total commissions, fees and other revenue	-13	-12	-29	-31
Intersegment elimination [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Total revenue	-13	-8	-36	-21
Total commissions, fees and other revenue	-13	-8	-36	-21
Unallocated Expense [Member]	'	'	'	'
Segment Reporting Information	'	'	'	'
Operating income before income tax	($39)	($44)	($123)	($133)

Guarantee_of_Registered_Securi2

Guarantee of Registered Securities (Narrative) (Details)	Sep. 30, 2014
Aon plc [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Parent company's percentage ownership of guarantors	100.00%
3.50% senior notes due September 2015 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	3.50%
3.125% Senior notes due 2016 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	3.13%
5.00% Senior notes due September 2020 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	5.00%
8.205% Junior subordinated deferrable interest debentures due January 2027 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	8.21%
6.25% Senior notes due September 2040 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	6.25%
4.250% Senior notes due 2042 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	4.25%
4.45% notes due 2043 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	4.45%
4.00% notes due 2023 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	4.00%
2.875% notes due 2026 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	2.88%
3.50% Notes due June 2024 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	3.50%
4.60% notes due May 2044 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	4.60%
3.50% notes due 2024 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	3.50%
4.60% notes due 2044 [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Debt interest rate percentage	4.60%

Guarantee_of_Registered_Securi3

Guarantee of Registered Securities - Condensed Consolidating Statement of Income (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue	'	'	'	'
Commissions, fees and other	$2,873	$2,786	$8,727	$8,585
Fiduciary investment income	7	8	19	21
Total revenue	2,880	2,794	8,746	8,606
Expenses	'	'	'	'
Compensation and benefits	1,707	1,666	5,166	5,103
Other general expenses	756	764	2,249	2,347
Total operating expenses	2,463	2,430	7,415	7,450
Operating income	417	364	1,331	1,156
Interest income	3	3	7	6
Interest expense	-65	-53	-188	-153
Intercompany interest income (expense)	0	0	0	0
Other income	35	39	34	54
Income before income taxes	390	353	1,184	1,063
Income tax expense (benefit)	75	89	220	275
Income (loss) before equity in earnings of subsidiaries	315	264	964	788
Equity in earnings of subsidiaries, net of tax	0	0	0	0
Net income	315	264	964	788
Less: Net income attributable to noncontrolling interests	6	8	26	30
Net income attributable to Aon shareholders	309	256	938	758
Aon plc [Member]	'	'	'	'
Revenue	'	'	'	'
Commissions, fees and other	0	1	0	2
Fiduciary investment income	0	0	0	0
Total revenue	0	1	0	2
Expenses	'	'	'	'
Compensation and benefits	4	11	29	27
Other general expenses	6	0	18	14
Total operating expenses	10	11	47	41
Operating income	-10	-10	-47	-39
Interest income	-2	0	-6	1
Interest expense	-25	-6	-49	-12
Intercompany interest income (expense)	113	25	335	11
Other income	2	0	1	0
Income before income taxes	78	9	234	-39
Income tax expense (benefit)	16	-2	49	-11
Income (loss) before equity in earnings of subsidiaries	62	11	185	-28
Equity in earnings of subsidiaries, net of tax	247	245	753	786
Net income	309	256	938	758
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Aon shareholders	309	256	938	758
Aon Corporation [Member]	'	'	'	'
Revenue	'	'	'	'
Commissions, fees and other	0	0	0	0
Fiduciary investment income	0	0	0	0
Total revenue	0	0	0	0
Expenses	'	'	'	'
Compensation and benefits	5	14	19	34
Other general expenses	14	5	37	29
Total operating expenses	19	19	56	63
Operating income	-19	-19	-56	-63
Interest income	1	1	1	2
Interest expense	-42	-39	-105	-106
Intercompany interest income (expense)	-73	11	-220	96
Other income	2	13	10	10
Income before income taxes	-131	-33	-370	-61
Income tax expense (benefit)	-52	-14	-144	-24
Income (loss) before equity in earnings of subsidiaries	-79	-19	-226	-37
Equity in earnings of subsidiaries, net of tax	202	127	734	617
Net income	123	108	508	580
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Aon shareholders	123	108	508	580
Other Non-Guarantor Subsidiaries [Member]	'	'	'	'
Revenue	'	'	'	'
Commissions, fees and other	2,873	2,785	8,727	8,583
Fiduciary investment income	7	8	19	21
Total revenue	2,880	2,793	8,746	8,604
Expenses	'	'	'	'
Compensation and benefits	1,698	1,641	5,118	5,042
Other general expenses	736	759	2,194	2,304
Total operating expenses	2,434	2,400	7,312	7,346
Operating income	446	393	1,434	1,258
Interest income	4	2	12	3
Interest expense	2	-8	-34	-35
Intercompany interest income (expense)	-40	-36	-115	-107
Other income	31	26	23	44
Income before income taxes	443	377	1,320	1,163
Income tax expense (benefit)	111	105	315	310
Income (loss) before equity in earnings of subsidiaries	332	272	1,005	853
Equity in earnings of subsidiaries, net of tax	0	0	0	0
Net income	332	272	1,005	853
Less: Net income attributable to noncontrolling interests	6	8	26	30
Net income attributable to Aon shareholders	326	264	979	823
Consolidating Adjustments [Member]	'	'	'	'
Revenue	'	'	'	'
Commissions, fees and other	0	0	0	0
Fiduciary investment income	0	0	0	0
Total revenue	0	0	0	0
Expenses	'	'	'	'
Compensation and benefits	0	0	0	0
Other general expenses	0	0	0	0
Total operating expenses	0	0	0	0
Operating income	0	0	0	0
Interest income	0	0	0	0
Interest expense	0	0	0	0
Intercompany interest income (expense)	0	0	0	0
Other income	0	0	0	0
Income before income taxes	0	0	0	0
Income tax expense (benefit)	0	0	0	0
Income (loss) before equity in earnings of subsidiaries	0	0	0	0
Equity in earnings of subsidiaries, net of tax	-449	-372	-1,487	-1,403
Net income	-449	-372	-1,487	-1,403
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Aon shareholders	($449)	($372)	($1,487)	($1,403)

Guarantee_of_Registered_Securi4

Guarantee of Registered Securities - Condensed Consolidating Statement of Comprehensive Income (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Net income	$315	$264	$964	$788
Less: Net income attributable to noncontrolling interests	6	8	26	30
Net income attributable to Aon shareholders	309	256	938	758
Change in fair value of investments	0	-14	-1	-1
Change in fair value of derivatives	-8	9	13	-12
Foreign currency translation adjustments	-318	155	-228	-77
Post-retirement benefit obligation	26	24	70	65
Total other comprehensive (loss) income	-300	174	-146	-25
Equity in other comprehensive loss of subsidiaries, net of tax	0	0	0	0
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	3	-2	1
Total other comprehensive (loss) income attributable to Aon shareholders	-300	171	-144	-26
Comprehensive income attributable to Aon shareholders	9	427	794	732
Aon plc [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Net income	309	256	938	758
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Aon shareholders	309	256	938	758
Change in fair value of investments	0	0	0	0
Change in fair value of derivatives	0	0	0	0
Foreign currency translation adjustments	0	0	0	0
Post-retirement benefit obligation	0	0	0	0
Total other comprehensive (loss) income	0	0	0	0
Equity in other comprehensive loss of subsidiaries, net of tax	-300	170	-144	-27
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	0	0	0
Total other comprehensive (loss) income attributable to Aon shareholders	-300	170	-144	-27
Comprehensive income attributable to Aon shareholders	9	426	794	731
Aon Corporation [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Net income	123	108	508	580
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Aon shareholders	123	108	508	580
Change in fair value of investments	0	-4	0	0
Change in fair value of derivatives	-1	2	-1	5
Foreign currency translation adjustments	-17	6	-19	-14
Post-retirement benefit obligation	6	7	17	22
Total other comprehensive (loss) income	-12	11	-3	13
Equity in other comprehensive loss of subsidiaries, net of tax	-285	157	-142	-38
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	0	0	0
Total other comprehensive (loss) income attributable to Aon shareholders	-297	168	-145	-25
Comprehensive income attributable to Aon shareholders	-174	276	363	555
Other Non-Guarantor Subsidiaries [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Net income	332	272	1,005	853
Less: Net income attributable to noncontrolling interests	6	8	26	30
Net income attributable to Aon shareholders	326	264	979	823
Change in fair value of investments	0	-10	-1	-1
Change in fair value of derivatives	-7	7	14	-17
Foreign currency translation adjustments	-301	149	-209	-63
Post-retirement benefit obligation	20	17	53	43
Total other comprehensive (loss) income	-288	163	-143	-38
Equity in other comprehensive loss of subsidiaries, net of tax	0	0	0	0
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	3	-2	1
Total other comprehensive (loss) income attributable to Aon shareholders	-288	160	-141	-39
Comprehensive income attributable to Aon shareholders	38	424	838	784
Consolidating Adjustments [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Net income	-449	-372	-1,487	-1,403
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Aon shareholders	-449	-372	-1,487	-1,403
Change in fair value of investments	0	0	0	0
Change in fair value of derivatives	0	0	0	0
Foreign currency translation adjustments	0	0	0	0
Post-retirement benefit obligation	0	0	0	0
Total other comprehensive (loss) income	0	0	0	0
Equity in other comprehensive loss of subsidiaries, net of tax	585	-327	286	65
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	0	0	0
Total other comprehensive (loss) income attributable to Aon shareholders	585	-327	286	65
Comprehensive income attributable to Aon shareholders	$136	($699)	($1,201)	($1,338)

Guarantee_of_Registered_Securi5

Guarantee of Registered Securities - Condensed Consolidating Statement of Financial Position (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
CURRENT ASSETS :	'	'	'	'
Cash and cash equivalents	$382	$477	$369	$291
Short-term investments	217	523	'	'
Receivables, net	2,630	2,896	'	'
Fiduciary assets	10,815	11,871	'	'
Intercompany receivables	0	0	'	'
Other current assets	711	563	'	'
Total Current Assets	14,755	16,330	'	'
Goodwill	9,026	8,997	'	'
Intangible assets, net	2,612	2,578	'	'
Fixed assets, net	760	791	'	'
Investments	143	132	'	'
Intercompany receivables	0	0	'	'
Other non-current assets	1,531	1,423	'	'
Investment in subsidiary	0	0	'	'
TOTAL ASSETS	28,827	30,251	'	'
CURRENT LIABILITIES	'	'	'	'
Fiduciary liabilities	10,815	11,871	'	'
Short-term debt and current portion of long-term debt	660	703	'	'
Accounts payable and accrued liabilities	1,528	1,931	'	'
Intercompany payables	0	0	'	'
Other current liabilities	853	906	'	'
Total Current Liabilities	13,856	15,411	'	'
Long-term debt	4,840	3,686	'	'
Pension, other post-retirement and other post-employment liabilities	1,437	1,607	'	'
Intercompany payables	0	0	'	'
Other non-current liabilities	1,422	1,352	'	'
TOTAL LIABILITIES	21,555	22,056	'	'
TOTAL AON SHAREHOLDERS' EQUITY	7,215	8,145	'	'
Noncontrolling interests	57	50	'	'
TOTAL EQUITY	7,272	8,195	'	'
TOTAL LIABILITIES AND EQUITY	28,827	30,251	'	'
Aon plc [Member]	'	'	'	'
CURRENT ASSETS :	'	'	'	'
Cash and cash equivalents	0	0	118	131
Short-term investments	0	0	'	'
Receivables, net	0	0	'	'
Fiduciary assets	0	0	'	'
Intercompany receivables	321	186	'	'
Other current assets	1	0	'	'
Total Current Assets	322	186	'	'
Goodwill	0	0	'	'
Intangible assets, net	0	0	'	'
Fixed assets, net	0	0	'	'
Investments	0	0	'	'
Intercompany receivables	7,408	7,166	'	'
Other non-current assets	169	146	'	'
Investment in subsidiary	5,752	4,607	'	'
TOTAL ASSETS	13,651	12,105	'	'
CURRENT LIABILITIES	'	'	'	'
Fiduciary liabilities	0	0	'	'
Short-term debt and current portion of long-term debt	0	0	'	'
Accounts payable and accrued liabilities	1,683	1,036	'	'
Intercompany payables	8	15	'	'
Other current liabilities	72	12	'	'
Total Current Liabilities	1,763	1,063	'	'
Long-term debt	2,568	792	'	'
Pension, other post-retirement and other post-employment liabilities	0	0	'	'
Intercompany payables	2,100	2,100	'	'
Other non-current liabilities	5	5	'	'
TOTAL LIABILITIES	6,436	3,960	'	'
TOTAL AON SHAREHOLDERS' EQUITY	7,215	8,145	'	'
Noncontrolling interests	0	0	'	'
TOTAL EQUITY	7,215	8,145	'	'
TOTAL LIABILITIES AND EQUITY	13,651	12,105	'	'
Aon Corporation [Member]	'	'	'	'
CURRENT ASSETS :	'	'	'	'
Cash and cash equivalents	568	247	291	199
Short-term investments	59	163	'	'
Receivables, net	0	4	'	'
Fiduciary assets	0	0	'	'
Intercompany receivables	2,696	3,503	'	'
Other current assets	205	69	'	'
Total Current Assets	3,528	3,986	'	'
Goodwill	0	0	'	'
Intangible assets, net	0	0	'	'
Fixed assets, net	0	0	'	'
Investments	79	57	'	'
Intercompany receivables	2,162	2,178	'	'
Other non-current assets	498	560	'	'
Investment in subsidiary	16,469	11,694	'	'
TOTAL ASSETS	22,736	18,475	'	'
CURRENT LIABILITIES	'	'	'	'
Fiduciary liabilities	0	0	'	'
Short-term debt and current portion of long-term debt	649	0	'	'
Accounts payable and accrued liabilities	34	62	'	'
Intercompany payables	9,258	5,449	'	'
Other current liabilities	47	47	'	'
Total Current Liabilities	9,988	5,558	'	'
Long-term debt	1,917	2,512	'	'
Pension, other post-retirement and other post-employment liabilities	854	925	'	'
Intercompany payables	7,277	7,267	'	'
Other non-current liabilities	108	159	'	'
TOTAL LIABILITIES	20,144	16,421	'	'
TOTAL AON SHAREHOLDERS' EQUITY	2,592	2,054	'	'
Noncontrolling interests	0	0	'	'
TOTAL EQUITY	2,592	2,054	'	'
TOTAL LIABILITIES AND EQUITY	22,736	18,475	'	'
Other Non-Guarantor Subsidiaries [Member]	'	'	'	'
CURRENT ASSETS :	'	'	'	'
Cash and cash equivalents	1,444	1,246	0	0
Short-term investments	158	360	'	'
Receivables, net	2,633	2,892	'	'
Fiduciary assets	10,815	11,871	'	'
Intercompany receivables	9,419	5,452	'	'
Other current assets	669	513	'	'
Total Current Assets	25,138	22,334	'	'
Goodwill	9,026	8,997	'	'
Intangible assets, net	2,612	2,578	'	'
Fixed assets, net	760	791	'	'
Investments	64	75	'	'
Intercompany receivables	2,211	2,201	'	'
Other non-current assets	1,550	1,421	'	'
Investment in subsidiary	0	0	'	'
TOTAL ASSETS	41,361	38,397	'	'
CURRENT LIABILITIES	'	'	'	'
Fiduciary liabilities	10,815	11,871	'	'
Short-term debt and current portion of long-term debt	11	707	'	'
Accounts payable and accrued liabilities	1,444	1,849	'	'
Intercompany payables	3,170	3,677	'	'
Other current liabilities	898	866	'	'
Total Current Liabilities	16,338	18,970	'	'
Long-term debt	355	378	'	'
Pension, other post-retirement and other post-employment liabilities	583	682	'	'
Intercompany payables	2,404	2,178	'	'
Other non-current liabilities	1,995	1,892	'	'
TOTAL LIABILITIES	21,675	24,100	'	'
TOTAL AON SHAREHOLDERS' EQUITY	19,629	14,247	'	'
Noncontrolling interests	57	50	'	'
TOTAL EQUITY	19,686	14,297	'	'
TOTAL LIABILITIES AND EQUITY	41,361	38,397	'	'
Consolidating Adjustments [Member]	'	'	'	'
CURRENT ASSETS :	'	'	'	'
Cash and cash equivalents	-1,630	-1,016	-40	-39
Short-term investments	0	0	'	'
Receivables, net	-3	0	'	'
Fiduciary assets	0	0	'	'
Intercompany receivables	-12,436	-9,141	'	'
Other current assets	-164	-19	'	'
Total Current Assets	-14,233	-10,176	'	'
Goodwill	0	0	'	'
Intangible assets, net	0	0	'	'
Fixed assets, net	0	0	'	'
Investments	0	0	'	'
Intercompany receivables	-11,781	-11,545	'	'
Other non-current assets	-686	-704	'	'
Investment in subsidiary	-22,221	-16,301	'	'
TOTAL ASSETS	-48,921	-38,726	'	'
CURRENT LIABILITIES	'	'	'	'
Fiduciary liabilities	0	0	'	'
Short-term debt and current portion of long-term debt	0	-4	'	'
Accounts payable and accrued liabilities	-1,633	-1,016	'	'
Intercompany payables	-12,436	-9,141	'	'
Other current liabilities	-164	-19	'	'
Total Current Liabilities	-14,233	-10,180	'	'
Long-term debt	0	4	'	'
Pension, other post-retirement and other post-employment liabilities	0	0	'	'
Intercompany payables	-11,781	-11,545	'	'
Other non-current liabilities	-686	-704	'	'
TOTAL LIABILITIES	-26,700	-22,425	'	'
TOTAL AON SHAREHOLDERS' EQUITY	-22,221	-16,301	'	'
Noncontrolling interests	0	0	'	'
TOTAL EQUITY	-22,221	-16,301	'	'
TOTAL LIABILITIES AND EQUITY	($48,921)	($38,726)	'	'

Guarantee_of_Registered_Securi6

Guarantee of Registered Securities - Condensed Consolidating Statement of Cash Flows (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	$883	$984
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Proceeds from sale of long-term investments	51	81
Purchases of long-term investments	-19	-13
Net sales of short-term investments - non-fiduciary	301	-13
Acquisition of businesses, net of cash acquired	-464	-26
Proceeds from sale of businesses	48	6
Capital expenditures	-179	-174
CASH USED FOR INVESTING ACTIVITIES	-262	-139
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Share repurchase	-1,750	-1,025
Advances (to) from affiliates	0	0
Issuance of shares for employee benefit plans	58	84
Issuance of debt	4,255	4,270
Repayment of debt	-3,073	-3,870
Cash dividends to shareholders	-201	-159
Purchase of shares from noncontrolling interests	1	-6
Dividends paid to noncontrolling interests	-18	-13
Proceeds from sale-leaseback	25	0
CASH USED FOR FINANCING ACTIVITIES	-703	-719
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	-13	-48
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	-95	78
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	477	291
CASH AND CASH EQUIVALENTS AT END OF PERIOD	382	369
Aon plc [Member]	'	'
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	309	-14
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Proceeds from sale of long-term investments	0	0
Purchases of long-term investments	0	0
Net sales of short-term investments - non-fiduciary	0	0
Acquisition of businesses, net of cash acquired	0	0
Proceeds from sale of businesses	0	0
Capital expenditures	0	0
CASH USED FOR INVESTING ACTIVITIES	0	0
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Share repurchase	-1,750	-1,025
Advances (to) from affiliates	-253	405
Issuance of shares for employee benefit plans	58	84
Issuance of debt	2,714	1,145
Repayment of debt	-877	-449
Cash dividends to shareholders	-201	-159
Purchase of shares from noncontrolling interests	0	0
Dividends paid to noncontrolling interests	0	0
Proceeds from sale-leaseback	0	'
CASH USED FOR FINANCING ACTIVITIES	-309	1
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	-13
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	0	131
CASH AND CASH EQUIVALENTS AT END OF PERIOD	0	118
Aon Corporation [Member]	'	'
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	-348	-195
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Proceeds from sale of long-term investments	39	8
Purchases of long-term investments	-19	-13
Net sales of short-term investments - non-fiduciary	103	-35
Acquisition of businesses, net of cash acquired	0	0
Proceeds from sale of businesses	0	0
Capital expenditures	0	0
CASH USED FOR INVESTING ACTIVITIES	123	-40
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Share repurchase	0	0
Advances (to) from affiliates	496	610
Issuance of shares for employee benefit plans	0	0
Issuance of debt	1,541	2,894
Repayment of debt	-1,491	-3,177
Cash dividends to shareholders	0	0
Purchase of shares from noncontrolling interests	0	0
Dividends paid to noncontrolling interests	0	0
Proceeds from sale-leaseback	0	'
CASH USED FOR FINANCING ACTIVITIES	546	327
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	321	92
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	247	199
CASH AND CASH EQUIVALENTS AT END OF PERIOD	568	291
Other Non-Guarantor Subsidiaries [Member]	'	'
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	922	1,193
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Proceeds from sale of long-term investments	12	73
Purchases of long-term investments	0	0
Net sales of short-term investments - non-fiduciary	198	22
Acquisition of businesses, net of cash acquired	-464	-26
Proceeds from sale of businesses	48	6
Capital expenditures	-179	-174
CASH USED FOR INVESTING ACTIVITIES	-385	-99
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Share repurchase	0	0
Advances (to) from affiliates	371	-1,014
Issuance of shares for employee benefit plans	0	0
Issuance of debt	0	231
Repayment of debt	-705	-244
Cash dividends to shareholders	0	0
Purchase of shares from noncontrolling interests	1	-6
Dividends paid to noncontrolling interests	-18	-13
Proceeds from sale-leaseback	25	'
CASH USED FOR FINANCING ACTIVITIES	-326	-1,046
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	-13	-48
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	198	0
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	1,246	0
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,444	0
Consolidating Adjustments [Member]	'	'
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
CASH PROVIDED BY (USED FOR) OPERATING ACTIVITIES	0	0
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Proceeds from sale of long-term investments	0	0
Purchases of long-term investments	0	0
Net sales of short-term investments - non-fiduciary	0	0
Acquisition of businesses, net of cash acquired	0	0
Proceeds from sale of businesses	0	0
Capital expenditures	0	0
CASH USED FOR INVESTING ACTIVITIES	0	0
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Share repurchase	0	0
Advances (to) from affiliates	-614	-1
Issuance of shares for employee benefit plans	0	0
Issuance of debt	0	0
Repayment of debt	0	0
Cash dividends to shareholders	0	0
Purchase of shares from noncontrolling interests	0	0
Dividends paid to noncontrolling interests	0	0
Proceeds from sale-leaseback	0	'
CASH USED FOR FINANCING ACTIVITIES	-614	-1
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	-614	-1
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	-1,016	-39
CASH AND CASH EQUIVALENTS AT END OF PERIOD	($1,630)	($40)