v2.4.0.6

Lease Commitments (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Lease Commitments |  |  |
Percentage of Aon's lease obligations for the use of office space | 88.00% |  |
Rental expenses for operating leases |  |  |
Rental expense | $ 525 | $ 429 | $ 346
Sub lease rental income | 71 | 57 | 52
Net rental expense | 454 | 372 | 294
Future minimum rental payments under operating leases |  |  |
2012 | 395 |  |
2013 | 373 |  |
2014 | 334 |  |
2015 | 296 |  |
2016 | 257 |  |
Thereafter | 984 |  |
Total minimum payments required | $ 2,639 |  |

X
- Definition For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date, net of sublease rental income, relating to leases defined as operating. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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X
- Definition The total of future contractually required payments, net of sublease rental income, on leases defined as operating. + References No definition available. + Details
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X
- Definition For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due within the fifth year of the balance sheet date relating to leases defined as operating. + References No definition available. + Details
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X
- Definition For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due within the fifth year of the balance sheet date relating to leases defined as operating. + References No definition available. + Details
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X
- Definition For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income due within the third year of the balance sheet date relating to leases defined as operating. + References No definition available. + Details
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X
- Definition For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due after the fifth year from the balance sheet date on leases defined as operating. + References No definition available. + Details
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X
- Definition For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due within the second year of the balance sheet date relating to leases defined as operating. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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X
- Definition Represents the percentage of entity's lease obligations for the use of office space. + References No definition available. + Details
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Namespace Prefix: | aon_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rental expense incurred for leased assets including furniture and equipment which has not been recognized in costs and expenses applicable to sales and revenues; for example, cost of goods sold or other operating costs and expenses. + References No definition available. + Details
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- Details
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- Details
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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717 + Details
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- Definition The total amount of sublease rental income recognized during the period that reduces the entity's rent expense incurred under operating leases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -Name Accounting Standards Codification -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 + Details
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