XML 115 R74.htm IDEA: XBRL DOCUMENT
v3.20.1

Fair Value Measurements and Financial Instruments - Schedule of assets and liabilities that are measured at fair value on a recurring basis (Details) - Recurring - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Money market funds and highly liquid debt securities |  |
Assets |  |
Money market funds and highly liquid debt securities | $ 2,252 | $ 2,007
Government bonds |  |
Assets |  |
Other investments | 1 | 1
Equity investments |  |
Assets |  |
Other investments | 1 | 1
Gross foreign exchange contracts |  |
Assets |  |
Derivatives | 13 | 21
Liabilities |  |
Derivatives | 5 | 4
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds and highly liquid debt securities |  |
Assets |  |
Money market funds and highly liquid debt securities | 2,252 | 2,007
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government bonds |  |
Assets |  |
Other investments | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity investments |  |
Assets |  |
Other investments | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Gross foreign exchange contracts |  |
Assets |  |
Derivatives | 0 | 0
Liabilities |  |
Derivatives | 0 | 0
Significant Other Observable Inputs (Level 2) | Money market funds and highly liquid debt securities |  |
Assets |  |
Money market funds and highly liquid debt securities | 0 | 0
Significant Other Observable Inputs (Level 2) | Government bonds |  |
Assets |  |
Other investments | 1 | 1
Significant Other Observable Inputs (Level 2) | Equity investments |  |
Assets |  |
Other investments | 1 | 1
Significant Other Observable Inputs (Level 2) | Gross foreign exchange contracts |  |
Assets |  |
Derivatives | 13 | 21
Liabilities |  |
Derivatives | 5 | 4
Significant Unobservable Inputs (Level 3) | Money market funds and highly liquid debt securities |  |
Assets |  |
Money market funds and highly liquid debt securities | 0 | 0
Significant Unobservable Inputs (Level 3) | Government bonds |  |
Assets |  |
Other investments | 0 | 0
Significant Unobservable Inputs (Level 3) | Equity investments |  |
Assets |  |
Other investments | 0 | 0
Significant Unobservable Inputs (Level 3) | Gross foreign exchange contracts |  |
Assets |  |
Derivatives | 0 | 0
Liabilities |  |
Derivatives | $ 0 | $ 0

X
- Definition Represents the fair value of money market funds and other highly liquid securities. + References No definition available. + Details
Name: | aon_BasisMoneyMarketFundsAndHighlyLiquidSecuritiesFairValueDisclosure
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AssetsFairValueDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
Name: | us-gaap_DerivativeAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + Details
Name: | us-gaap_DerivativeLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_LiabilitiesFairValueDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investments classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_OtherInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=aon_MoneyMarketFundsAndOtherHighlyLiquidDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=aon_GovernmentBondSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignExchangeContractMember
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: |