XML 43 R1.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Cover - USD ($) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2023 | Apr. 12, 2024 | Jun. 30, 2023
Document Information [Line Items] |  |  |
Document Type | 10-K/A |  |
Document Annual Report | true |  |
Document Period End Date | Dec. 31, 2023 |  |
Current Fiscal Year End Date | --12-31 |  |
Document Transition Report | false |  |
Entity File Number | 1-7933 |  |
Entity Registrant Name | Aon plc |  |
Entity Incorporation, State or Country Code | L2 |  |
Entity Tax Identification Number | 98-1539969 |  |
Entity Address, Address Line One | Metropolitan Building, James Joyce Street |  |
Entity Address, City or Town | Dublin 1 |  |
Entity Address, Country | IE |  |
Entity Address, Postal Zip Code | D01 K0Y8 |  |
Country Region | 353 |  |
City Area Code | 1 |  |
Local Phone Number | 266 6000 |  |
Entity Well-known Seasoned Issuer | Yes |  |
Entity Voluntary Filers | No |  |
Entity Current Reporting Status | Yes |  |
Entity Interactive Data Current | Yes |  |
Entity Filer Category | Large Accelerated Filer |  |
Entity Small Business | false |  |
Entity Emerging Growth Company | false |  |
ICFR Auditor Attestation Flag | true |  |
Document Financial Statement Error Correction [Flag] | false |  |
Entity Shell Company | false |  |
Entity Public Float |  |  | $ 70,135,237,097
Entity Common Stock, Shares Outstanding |  | 198,506,718 |
Documents Incorporated by Reference [Text Block] | None |  |
Entity Central Index Key | 0000315293 |  |
Amendment Flag | true |  |
Document Fiscal Year Focus | 2023 |  |
Document Fiscal Period Focus | FY |  |
Amendment Description | This Amendment No. 1 on Form 10-K/A (this “Amendment”) amends our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, originally filed with the Securities and Exchange Commission (the “SEC”) on February 16, 2024 (the “Original Filing”). The Original Filing omitted Part III, Items 10 (Directors, Executive Officers and Corporate Governance), 11 (Executive Compensation), 12 (Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters), 13 (Certain Relationships and Related Transactions, and Director Independence) and 14 (Principal Accountant Fees and Services) in reliance on General Instruction G(3) to Form 10-K, which provides that such information may be either incorporated by reference from the registrant’s definitive proxy statement or included in an amendment to Form 10-K, in either case filed with the Securities and Exchange Commission (the “SEC”) not later than 120 days after the end of the fiscal year. We are filing this Amendment solely to amend Part III, Items 10, 11, 12, 13 and 14 of the Original Filing to include the information required by such Items.In addition, in connection with the filing of this Amendment and pursuant to the rules of the SEC, we are including with this Amendment new certifications of our principal executive officer and principal financial officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. Item 15 of Part IV has also been amended to reflect the filing of these new certifications.Except as described above, no other changes have been made to the Original Filing. The Original Filing continues to speak as of the date of the Original Filing, and we have not updated the disclosures contained therein to reflect any events which occurred at a date subsequent to the filing of the Original Filing.Unless otherwise indicated or unless the context requires otherwise, all references in this Amendment to “we,” “us,” “our,” “our Company” or “the Company” refer to Aon plc, an Irish public limited company, together with its consolidated subsidiaries.As previously announced, on December 19, 2023, Aon entered into a definitive agreement with Randolph Acquisition Corp., a Delaware corporation and an indirect, wholly owned subsidiary of Aon (the “Acquirer”), Randolph Merger Sub LLC, a Delaware limited liability company and a direct, wholly owned subsidiary of the Acquirer, NFP Intermediate Holdings A Corp., a Delaware corporation (“NFP”), and NFP Parent Co, LLC, a Delaware limited liability company, pursuant to which the Acquirer will acquire NFP. |  |
Capital Unit, Class A [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Class A Ordinary Shares $0.01 nominal value |  |
Trading Symbol | AON |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 3.50 Senior Notes Due 2024 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 3.50% Senior Notes due 2024 |  |
Trading Symbol | AON24 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 3.875 Senior Notes Due 2025 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 3.875% Senior Notes due 2025 |  |
Trading Symbol | AON25 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 2.875 Senior Notes Due 2026 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 2.875% Senior Notes due 2026 |  |
Trading Symbol | AON26 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.85 Senior Notes Due 2027 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.85% Senior Notes due 2027 |  |
Trading Symbol | AON27 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.05 Senior Notes Due 2031 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.05% Senior Notes due 2031 |  |
Trading Symbol | AON31 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.60 Senior Notes Due 2031 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.60% Senior Notes due 2031 |  |
Trading Symbol | AON31A |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 5.00 Senior Notes Due 2032 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.00% Senior Notes due 2032 |  |
Trading Symbol | AON32 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 5.35 Senior Notes Due 2033 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.35% Senior Notes due 2033 |  |
Trading Symbol | AON33 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 4.25 Senior Notes Due 2042 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 4.25% Senior Notes due 2042 |  |
Trading Symbol | AON42 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 4.45 Senior Notes Due 2043 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 4.45% Senior Notes due 2043 |  |
Trading Symbol | AON43 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 4.60 Senior Notes Due 2044 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 4.60% Senior Notes due 2044 |  |
Trading Symbol | AON44 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Plcs 4.75 Senior Notes Due 2045 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon plc’s 4.75% Senior Notes due 2045 |  |
Trading Symbol | AON45 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.90 Senior Notes Due 2051 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.90% Senior Notes due 2051 |  |
Trading Symbol | AON51 |  |
Security Exchange Name | NYSE |  |
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 3.90 Senior Notes Due 2052 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.90% Senior Notes due 2052 |  |
Trading Symbol | AON52 |  |
Security Exchange Name | NYSE |  |
Guarantees of Aon North America Incs 5.125 Senior Notes due 2027 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon North America, Inc.’s 5.125% Senior Notes due 2027 |  |
Trading Symbol | AON27B |  |
Security Exchange Name | NYSE |  |
Guarantees of Aon North America Incs 5.150 Senior Notes due 2029 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon North America, Inc.’s 5.150% Senior Notes due 2029 |  |
Trading Symbol | AON29 |  |
Security Exchange Name | NYSE |  |
Guarantees of Aon North America Incs 5.300 Senior Notes due 2031 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon North America, Inc.’s 5.300% Senior Notes due 2031 |  |
Trading Symbol | AON31B |  |
Security Exchange Name | NYSE |  |
Guarantees of Aon North America Incs 5.450 Senior Notes due 2034 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon North America, Inc.’s 5.450% Senior Notes due 2034 |  |
Trading Symbol | AON34 |  |
Security Exchange Name | NYSE |  |
Guarantees of Aon North America Incs 5.750 Senior Notes due 2054 [Member] |  |  |
Document Information [Line Items] |  |  |
Title of 12(b) Security | Guarantees of Aon North America, Inc.’s 5.750% Senior Notes due 2054 |  |
Trading Symbol | AON54 |  |
Security Exchange Name | NYSE |  |

X
- Definition Description of changes contained within amended document. + References No definition available. + Details
Name: | dei_AmendmentDescription
Namespace Prefix: | dei_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Boolean flag that is true when the XBRL content amends previously-filed or accepted submission. + References No definition available. + Details
Name: | dei_AmendmentFlag
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition Area code of city + References No definition available. + Details
Name: | dei_CityAreaCode
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Region code of country + References No definition available. + Details
Name: | dei_CountryRegion
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition End date of current fiscal year in the format --MM-DD. + References No definition available. + Details
Name: | dei_CurrentFiscalYearEndDate
Namespace Prefix: | dei_
Data Type: | xbrli:gMonthDayItemType
Balance Type: | na
Period Type: | duration

X
- Definition Boolean flag that is true only for a form used as an annual report. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_DocumentAnnualReport
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicates whether any of the financial statement period in the filing include a restatement due to error correction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection w Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_DocumentFinStmtErrorCorrectionFlag
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fiscal period values are FY, Q1, Q2, and Q3. 1st, 2nd and 3rd quarter 10-Q or 10-QT statements have value Q1, Q2, and Q3 respectively, with 10-K, 10-KT or other fiscal year statements having FY. + References No definition available. + Details
Name: | dei_DocumentFiscalPeriodFocus
Namespace Prefix: | dei_
Data Type: | dei:fiscalPeriodItemType
Balance Type: | na
Period Type: | duration

X
- Definition This is focus fiscal year of the document report in YYYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006. + References No definition available. + Details
Name: | dei_DocumentFiscalYearFocus
Namespace Prefix: | dei_
Data Type: | xbrli:gYearItemType
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 No definition available. + Details
Name: | dei_DocumentInformationLineItems
Namespace Prefix: | dei_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD. + References No definition available. + Details
Name: | dei_DocumentPeriodEndDate
Namespace Prefix: | dei_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Boolean flag that is true only for a form used as a transition report. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Forms 10-K, 10-Q, 20-F -Number 240 -Section 13 -Subsection a-1 + Details
Name: | dei_DocumentTransitionReport
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'. + References No definition available. + Details
Name: | dei_DocumentType
Namespace Prefix: | dei_
Data Type: | dei:submissionTypeItemType
Balance Type: | na
Period Type: | duration

X
- Definition Documents incorporated by reference. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-23 + Details
Name: | dei_DocumentsIncorporatedByReferenceTextBlock
Namespace Prefix: | dei_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Address Line 1 such as Attn, Building Name, Street Name + References No definition available. + Details
Name: | dei_EntityAddressAddressLine1
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Name of the City or Town + References No definition available. + Details
Name: | dei_EntityAddressCityOrTown
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition ISO 3166-1 alpha-2 country code. + References No definition available. + Details
Name: | dei_EntityAddressCountry
Namespace Prefix: | dei_
Data Type: | dei:countryCodeItemType
Balance Type: | na
Period Type: | duration

X
- Definition Code for the postal or zip code + References No definition available. + Details
Name: | dei_EntityAddressPostalZipCode
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntityCentralIndexKey
Namespace Prefix: | dei_
Data Type: | dei:centralIndexKeyItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument. + References No definition available. + Details
Name: | dei_EntityCommonStockSharesOutstanding
Namespace Prefix: | dei_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure. + References No definition available. + Details
Name: | dei_EntityCurrentReportingStatus
Namespace Prefix: | dei_
Data Type: | dei:yesNoItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicate if registrant meets the emerging growth company criteria. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntityEmergingGrowthCompany
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen. + References No definition available. + Details
Name: | dei_EntityFileNumber
Namespace Prefix: | dei_
Data Type: | dei:fileNumberItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntityFilerCategory
Namespace Prefix: | dei_
Data Type: | dei:filerCategoryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Two-character EDGAR code representing the state or country of incorporation. + References No definition available. + Details
Name: | dei_EntityIncorporationStateCountryCode
Namespace Prefix: | dei_
Data Type: | dei:edgarStateCountryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-T -Number 232 -Section 405 + Details
Name: | dei_EntityInteractiveDataCurrent
Namespace Prefix: | dei_
Data Type: | dei:yesNoItemType
Balance Type: | na
Period Type: | duration

X
- Definition The aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant's most recently completed second fiscal quarter. + References No definition available. + Details
Name: | dei_EntityPublicFloat
Namespace Prefix: | dei_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntityRegistrantName
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntityShellCompany
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicates that the company is a Smaller Reporting Company (SRC). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntitySmallBusiness
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2 + Details
Name: | dei_EntityTaxIdentificationNumber
Namespace Prefix: | dei_
Data Type: | dei:employerIdItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicate 'Yes' or 'No' if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. + References No definition available. + Details
Name: | dei_EntityVoluntaryFilers
Namespace Prefix: | dei_
Data Type: | dei:yesNoItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicate 'Yes' or 'No' if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Is used on Form Type: 10-K, 10-Q, 8-K, 20-F, 6-K, 10-K/A, 10-Q/A, 20-F/A, 6-K/A, N-CSR, N-Q, N-1A. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Securities Act -Number 230 -Section 405 + Details
Name: | dei_EntityWellKnownSeasonedIssuer
Namespace Prefix: | dei_
Data Type: | dei:yesNoItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_IcfrAuditorAttestationFlag
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition Local phone number for entity. + References No definition available. + Details
Name: | dei_LocalPhoneNumber
Namespace Prefix: | dei_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Title of a 12(b) registered security. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b + Details
Name: | dei_Security12bTitle
Namespace Prefix: | dei_
Data Type: | dei:securityTitleItemType
Balance Type: | na
Period Type: | duration

X
- Definition Name of the Exchange on which a security is registered. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection d1-1 + Details
Name: | dei_SecurityExchangeName
Namespace Prefix: | dei_
Data Type: | dei:edgarExchangeCodeItemType
Balance Type: | na
Period Type: | duration

X
- Definition Trading symbol of an instrument as listed on an exchange. + References No definition available. + Details
Name: | dei_TradingSymbol
Namespace Prefix: | dei_
Data Type: | dei:tradingSymbolItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CapitalUnitClassAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs350SeniorNotesDue2024Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs3875SeniorNotesDue2025Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs2875SeniorNotesDue2026Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs2.85SeniorNotesDue2027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs2.05SeniorNotesDue2031Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs2.60SeniorNotesDue2031Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs5.00SeniorNotesDue2032Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs5.35SeniorNotesDue2033Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs425SeniorNotesDue2042Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs445SeniorNotesDue2043Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs460SeniorNotesDue2044Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonPlcs475SeniorNotesDue2045Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs290SeniorNotesDue2051Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonCorporationAndAonGlobalHoldingsPlcs390SeniorNotesDue2052Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonNorthAmericaIncs5.125SeniorNotesDue2027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonNorthAmericaIncs5.150SeniorNotesDue2029Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonNorthAmericaIncs5.300SeniorNotesDue2031Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonNorthAmericaIncs5.450SeniorNotesDue2034Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=aon_GuaranteesOfAonNorthAmericaIncs5.750SeniorNotesDue2054Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |