XML 76 R53.htm IDEA: XBRL DOCUMENT
v3.20.4

Acquisitions and Dispositions of Businesses - Completed Acquisitions Narrative (Details) $ in Millions | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) numberOfAcquisition | Dec. 31, 2019 numberOfAcquisition | Apr. 06, 2020 | Jan. 31, 2020 | Jan. 03, 2020 | Jan. 01, 2020
Business Acquisition [Line Items] |  |  |  |  |  |
Number of business acquired under business combination | numberOfAcquisition | 6 | 3 |  |  |  |
Weighted average useful life | 6 years |  |  |  |  |
Revenues from acquisitions included in the Company's Consolidated Statement of Income | $ 44 |  |  |  |  |
Farmington Administrative Services LLC |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Percentage of capital acquired |  |  | 100.00% |  |  |
Cytelligence Inc. |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Percentage of capital acquired |  |  |  | 100.00% |  |
Cover Wallet Inc. |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Percentage of capital acquired |  |  |  |  | 100.00% |
TRIUM GmbH Insurance Broker |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Percentage of capital acquired |  |  |  |  |  | 100.00%
Assimedia SA |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Percentage of capital acquired |  |  |  |  |  | 100.00%
Apollo Conseilet Courtage |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Percentage of capital acquired |  |  |  |  |  | 100.00%
Other general expense |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Acquisition related costs | $ 7 |  |  |  |  |

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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275 + Details
Name: | us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
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: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460 + Details
Name: | us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The number of businesses acquired by the entity during the period. + References No definition available. + Details
Name: | us-gaap_NumberOfBusinessesAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

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

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

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

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

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

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=aon_OtherGeneralExpensesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |