XML 75 R51.htm IDEA: XBRL DOCUMENT
v3.25.2

Acquisitions and Dispositions of Businesses - Narrative (Details) shares in Millions, $ in Millions |  |  | 3 Months Ended | 6 Months Ended | 98 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 25, 2024 USD ($) shares | Mar. 01, 2024 USD ($) | Jun. 30, 2025 USD ($) acquisition disposition | Jun. 30, 2024 USD ($) acquisition disposition | Jun. 30, 2025 USD ($) acquisition disposition | Jun. 30, 2024 USD ($) disposition acquisition | Jun. 30, 2025 USD ($) | Jan. 01, 2025 | Dec. 31, 2024 USD ($) | May 01, 2017 USD ($)
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Number of business acquired under business combination | acquisition |  |  | 2 | 8 | 9 | 8 |  |  |  |
Issuance of debt |  | $ 6,000 |  |  |  |  |  |  |  |
Proceeds from long-term lines of credit | $ 2,000 |  |  |  |  |  |  |  |  |
Decrease in goodwill |  |  |  |  | $ 28 |  |  |  |  |
Goodwill |  |  | $ 16,024 |  | $ 16,024 |  | $ 16,024 |  | $ 15,234 |
Number of dispositions | disposition |  |  | 1 |  | 1 | 3 |  |  |  |
Gain from sales of businesses |  |  | $ 0 | $ 257 | $ 0 | $ 257 |  |  |  |
Gain on disposition of business |  |  |  | $ 257 |  | 257 |  |  |  |
Deferred consideration on divestiture |  |  | $ 88 |  | $ 108 | $ 82 | 192 |  |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | May 1, 2017 Divested Business |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Purchase price |  |  |  |  |  |  |  |  |  | $ 4,300
Deferred consideration |  |  |  |  |  |  |  |  |  | $ 500
Risk Capital |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Number of business acquired under business combination | acquisition |  |  | 1 | 5 | 7 | 5 |  |  |  |
Decrease in goodwill |  |  |  |  | $ 11 |  |  |  |  |
Goodwill |  |  | $ 9,421 |  | $ 9,421 |  | 9,421 |  | 8,785 |
Number of dispositions | disposition |  |  |  | 2 |  | 2 |  |  |  |
Human Capital |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Number of business acquired under business combination | acquisition |  |  | 1 | 3 | 2 | 3 |  |  |  |
Decrease in goodwill |  |  |  |  | $ 17 |  |  |  |  |
Goodwill |  |  | $ 6,603 |  | 6,603 |  | 6,603 |  | $ 6,449 |
Number of dispositions | disposition |  |  |  |  |  | 1 |  |  |  |
Griffiths & Armour |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Percentage of capital acquired |  |  |  |  |  |  |  | 100.00% |  |
NFP Acquisition |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Percentage of capital acquired | 100.00% |  |  |  |  |  |  |  |  |
Total consideration | $ 9,100 |  |  |  | 9,129 |  |  |  |  |
Cash | $ 3,200 |  |  |  | 3,247 |  |  |  |  |
Number of shares issued for acquisition (up to) | shares | 19 |  |  |  |  |  |  |  |  |
Equity interest issued or issuable, value | $ 5,900 |  |  |  |  |  |  |  |  |
Adjustments for cash and certain assumed liabilities | $ 3,900 |  |  |  |  |  |  |  |  |
Increase of intangible assets |  |  |  |  | 125 |  |  |  |  |
Decrease of acquired notes receivable |  |  |  |  | 107 |  |  |  |  |
Decrease of deferred tax liabilities |  |  |  |  | 110 |  |  |  |  |
Decrease in goodwill |  |  |  |  | 115 |  |  |  |  |
Goodwill |  |  | 6,838 |  | $ 6,838 |  | 6,838 |  |  |
Weighted average useful life |  |  |  |  | 19 years |  |  |  |  |
NFP Acquisition | Risk Capital |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Goodwill |  |  | 2,600 |  | $ 2,600 |  | 2,600 |  |  |
NFP Acquisition | Human Capital |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Goodwill |  |  | $ 4,200 |  | $ 4,200 |  | $ 4,200 |  |  |

X
- Definition Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Cash And Certain Liabilities + References No definition available. + Details
Name: | aon_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentCashAndCertainLiabilities
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Tax Liabilities + References No definition available. + Details
Name: | aon_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredTaxLiabilities
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Notes Receivable + References No definition available. + Details
Name: | aon_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNotesReceivable
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Deferred Consideration On Divestiture + References No definition available. + Details
Name: | aon_DeferredConsiderationOnDivestiture
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Disposal Group, Including Discontinued Operation, Deferred Consideration + References No definition available. + Details
Name: | aon_DisposalGroupIncludingDiscontinuedOperationDeferredConsideration
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Gain On Disposition of Business + References No definition available. + Details
Name: | aon_GainOnDispositionOfBusiness
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the number of entities disposed of by the reporting entity. + References No definition available. + Details
Name: | aon_NumberOfDispositions
Namespace Prefix: | aon_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 985 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481283/985-20-50-2 + Details
Name: | us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 + Details
Name: | us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of shares of equity interest issued or issuable by acquirer as part of consideration transferred in business combination. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 41 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-41 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 42 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-42 + Details
Name: | us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-4 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 47 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-47 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-5 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (f)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(1)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(1)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-2 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (f)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-3 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4 Reference 22: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-4 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 34: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-1 Reference 37: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 38: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 39: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 40: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 41: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 Reference 42: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 + Details
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of voting equity interest acquired in business combination. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 38 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-38 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-2 + Details
Name: | us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 41 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-41 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to intangibles acquired in connection with a business combination for which the initial accounting was incomplete. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4 + Details
Name: | us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation. + References No definition available. + Details
Name: | us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 810 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481203/810-10-50-1B + Details
Name: | us-gaap_GainLossOnSaleOfBusiness
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 24 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482548/350-20-55-24 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 41 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-41 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 740 -Name Accounting Standards Codification -Section 55 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478064/805-740-55-13 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 39 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-39 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 49 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-49 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 8: http://www.xbrl.org/2003/role/exampleRef -Topic 852 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481372/852-10-55-10 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(15)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482598/350-20-45-1 Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(10)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 14: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-4 + Details
Name: | us-gaap_Goodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase (decrease) from measurement period adjustment of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-4 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479907/805-20-50-4A Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-5 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 25 -Paragraph 16 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479405/805-10-25-16 + Details
Name: | us-gaap_GoodwillPurchaseAccountingAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of businesses acquired in business combination. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-7 + Details
Name: | us-gaap_NumberOfBusinessesAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479328/805-10-50-8 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 41 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479303/805-10-55-41 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-13 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-14 + Details
Name: | us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-14 + Details
Name: | us-gaap_ProceedsFromLongTermLinesOfCredit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=aon_May12017DivestedBusinessMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=aon_RiskCapitalSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=aon_HumanCapitalSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=aon_GriffithsArmourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=aon_NFPIntermediateHoldingsACorp.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |