XML 118 R92.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Employee Benefits - Schedule of Fair Value of U.S Plan Assets (Details) - Pension Plan - U.S. - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | $ 2,378 | $ 2,276 | $ 2,066
Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 93 | 79 |
Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 86 | 207 |
Equity derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 19 | 62 |
Equity investments, Pooled funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 548 | 640 |
Corporate bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 249 | 167 |
Government and agency bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 230 | 233 |
Fixed Income Investments, Pooled Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 838 | 543 |
Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 156 | 163 |
Alternative investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 159 | 182 |
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 371 | 788 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 93 | 79 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 86 | 207 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity investments, Pooled funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 90 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 192 | 200 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed Income Investments, Pooled Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 212 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Alternative investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 306 | 262 |
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Equity derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 19 | 62 |
Significant Other Observable Inputs (Level 2) | Equity investments, Pooled funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Corporate bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 249 | 167 |
Significant Other Observable Inputs (Level 2) | Government and agency bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 38 | 33 |
Significant Other Observable Inputs (Level 2) | Fixed Income Investments, Pooled Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Alternative investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Equity derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Equity investments, Pooled funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Corporate bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Government and agency bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Fixed Income Investments, Pooled Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Alternative investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined benefit plan, plan assets | $ 0 | $ 0 |

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: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanSponsorLocationAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aon_EquityDerivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aon_EquityInvestmentsPooledFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aon_GovernmentAndAgencyBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aon_FixedIncomeInvestmentsPooledFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aon_AlternativeInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |