v2.3.0.15

Restructuring (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended		9 Months Ended	12 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2011 Aon Hewitt Restructuring Plan	Sep. 30, 2011 Aon Hewitt Restructuring Plan	Dec. 31, 2010 Aon Hewitt Restructuring Plan	Sep. 30, 2011 Aon Hewitt Restructuring Plan Real estate lease realization	Sep. 30, 2011 Aon Hewitt Restructuring Plan Workforce reduction job	Sep. 30, 2011 Aon Hewitt Restructuring Plan Workforce reduction job	Dec. 31, 2010 Aon Hewitt Restructuring Plan Workforce reduction	Oct. 14, 2010 Aon Hewitt Restructuring Plan Workforce reduction job	Sep. 30, 2011 Aon Hewitt Restructuring Plan Lease consolidation	Sep. 30, 2011 Aon Hewitt Restructuring Plan Lease consolidation	Dec. 31, 2010 Aon Hewitt Restructuring Plan Lease consolidation	Sep. 30, 2011 Aon Hewitt Restructuring Plan Asset impairments	Sep. 30, 2011 Aon Hewitt Restructuring Plan Asset impairments	Sep. 30, 2011 Aon Hewitt Restructuring Plan Other costs associated with restructuring	Dec. 31, 2011 Aon Benfield Restructuring Plan	Sep. 30, 2011 Aon Benfield Restructuring Plan	Sep. 30, 2010 Aon Benfield Restructuring Plan	Sep. 30, 2011 Aon Benfield Restructuring Plan	Sep. 30, 2010 Aon Benfield Restructuring Plan	Dec. 31, 2010 Aon Benfield Restructuring Plan	Dec. 31, 2009 Aon Benfield Restructuring Plan	Sep. 30, 2011 Aon Benfield Restructuring Plan Workforce reduction job	Sep. 30, 2011 Aon Benfield Restructuring Plan Workforce reduction job	Dec. 31, 2010 Aon Benfield Restructuring Plan Workforce reduction	Dec. 31, 2009 Aon Benfield Restructuring Plan Workforce reduction	Dec. 31, 2008 Aon Benfield Restructuring Plan Workforce reduction job	Sep. 30, 2011 Aon Benfield Restructuring Plan Lease consolidation	Sep. 30, 2011 Aon Benfield Restructuring Plan Lease consolidation	Dec. 31, 2010 Aon Benfield Restructuring Plan Lease consolidation	Dec. 31, 2009 Aon Benfield Restructuring Plan Lease consolidation	Sep. 30, 2011 Aon Benfield Restructuring Plan Asset impairments	Dec. 31, 2010 Aon Benfield Restructuring Plan Asset impairments	Dec. 31, 2009 Aon Benfield Restructuring Plan Asset impairments	Sep. 30, 2011 Aon Benfield Restructuring Plan Other costs associated with restructuring	Sep. 30, 2011 Aon Benfield Restructuring Plan Other costs associated with restructuring	Dec. 31, 2010 Aon Benfield Restructuring Plan Other costs associated with restructuring	Dec. 31, 2009 Aon Benfield Restructuring Plan Other costs associated with restructuring	Dec. 31, 2008 Aon Benfield Restructuring Plan Original Estimate year	Sep. 30, 2011 2007 Restructuring Plan	Sep. 30, 2010 2007 Restructuring Plan	Sep. 30, 2011 2007 Restructuring Plan	Sep. 30, 2010 2007 Restructuring Plan
Restructuring and Related Cost
Number of jobs expected to be eliminated under the plan, low end of the range								1,500
Number of jobs expected to be eliminated under the plan, high end of the range								1,800
Number of jobs eliminated to date under the plan					1,030	1,030																715	715
Number of jobs expected to be eliminated under the plan																										875
Restructuring costs recorded in earnings to date																		$ 79
Estimated additional restructuring costs to be recorded in future earnings															28																							81
Period over which the expected cost will be incurred (in years)																																						3
Purchase price allocation																		53					32					20							1			104
Restructuring benefits																		2																					3		8
Reversal of restructuring liability accrued in prior periods																		18
Lease expenses																(2)		4																					2		5
Restructuring and related charges	26	80	52		15	39	49		8	33	3	3	7	1		3	5	(2)	20	26	55	3	14	15	38		(1)	(17)	7	14		2	2	1	1	2	1			3		95
Restructuring charges total to date		132				88				36			7	1				132					99					24			4				5						740
Estimated Total Cost for Restructuring Period		325		145		180				95			47	3				160					125					26			4				5			185
Restructuring charges paid total to date		$ 132

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- Definition

Of the overall amount paid for the acquisition of a business, represents the purchase price allocated specifically for restructuring costs.

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The expected number of positions to be eliminated as a result of restructuring activities.

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Represents the high end range of the expected number of positions to be eliminated as a result of restructuring activities.

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- Definition

Represents the low end range of the expected number of positions to be eliminated as a result of restructuring activities.

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The amount of estimated additional restructuring costs to be recorded as expenses in future periods.

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The number of positions eliminated during the period as a result of restructuring activities.

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Amount of costs paid to date for the specified type of restructuring cost.

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Represents the number of years over which the cumulative restructuring costs will be incurred.

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Amount of costs recorded in earnings to date for the specified type of restructuring cost.

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Represents the restructuring benefits as a result of reversing the restructuring liability accrued in prior periods.

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- Definition

Amount of costs incurred to date for the specified type of restructuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 146

-Paragraph 20



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 95-3



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

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Amount expected to be charged against earnings in the current and future periods for the specified restructuring cost.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 146

-Paragraph 20



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 95-3



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount charged against earnings in the period for incurred and estimated costs, excluding asset retirement obligations, associated with exit from or disposal of business activities or restructurings pursuant to a program that is planned and controlled by management, and materially changes either the scope of a business undertaken by an entity, or the manner in which that business is conducted.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

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Amount of any reversal and other adjustment made during the period to the amount of a previously accrued liability for a specified type of restructuring cost, excluding adjustments for costs incurred during the period, costs settled during the period, and foreign currency translation adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 95-3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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