XML 82 R59.htm IDEA: XBRL DOCUMENT
v3.20.4

Debt - Summary of outstanding debt (Details) | Dec. 31, 2020 USD ($) | Dec. 31, 2020 EUR (€) | May 12, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Nov. 15, 2019 USD ($) | May 02, 2019 USD ($)
--- | --- | --- | --- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 7,729,000,000 |  |  |  | $ 7,339,000,000 |  |
Less: Short-term debt and current portion of long-term debt | 448,000,000 |  |  |  | 712,000,000 |  |
Long-term debt | 7,281,000,000 |  |  |  | 6,627,000,000 |  |
Other |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | 48,000,000 |  |  |  | 1,000,000 |  |
Five Point Zero Zero Percent Senior Notes Due Twenty Twenty [Member] | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 0 |  |  |  | 600,000,000 |  |
Interest rate on debt | 5.00% | 5.00% |  |  |  |  |
2.80% Senior Notes due March 2021 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 400,000,000 |  |  |  | 399,000,000 |  |
Interest rate on debt | 2.80% | 2.80% |  | 2.80% |  |  |
Debt face value |  |  |  | $ 400,000,000 |  |  |
2.20% Senior Notes due November 2022 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 498,000,000 |  |  |  | 497,000,000 |  |
Interest rate on debt | 2.20% | 2.20% |  |  |  | 2.20% |
Debt face value |  |  |  |  |  | $ 500,000,000 |
4.00% Senior Notes due November 2023 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 349,000,000 |  |  |  | 348,000,000 |  |
Interest rate on debt | 4.00% | 4.00% |  |  |  |  |
3.50% Senior Notes due June 2024 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 597,000,000 |  |  |  | 597,000,000 |  |
Interest rate on debt | 3.50% | 3.50% |  |  |  |  |
3.875% Senior Notes due December 2025 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 747,000,000 |  |  |  | 746,000,000 |  |
Interest rate on debt | 3.875% | 3.875% |  |  |  |  |
2.875% Senior Notes due May 2026 (EUR 500M) | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 606,000,000 |  |  |  | 550,000,000 |  |
Interest rate on debt | 2.875% | 2.875% |  |  |  |  |
Debt face value | € |  | € 500,000,000 |  |  |  |  |
8.205% Junior Subordinated Notes due January 2027 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 521,000,000 |  |  |  | 521,000,000 |  |
Interest rate on debt | 8.205% | 8.205% |  |  |  |  |
4.50% Senior Notes due December 2028 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 347,000,000 |  |  |  | 346,000,000 |  |
Interest rate on debt | 4.50% | 4.50% |  |  |  |  |
3.75% Senior Notes due May 2029 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 744,000,000 |  |  |  | 744,000,000 |  |
Interest rate on debt | 3.75% | 3.75% |  |  |  |  | 3.75%
Debt face value |  |  |  |  |  |  | $ 750,000,000
2.80% Senior Notes due May 2030 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 992,000,000 |  |  |  | 0 |  |
Interest rate on debt | 2.80% | 2.80% | 2.80% |  |  |  |
Debt face value |  |  | $ 1,000,000,000 |  |  |  |
6.25% Senior Notes due September 2040 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 296,000,000 |  |  |  | 296,000,000 |  |
Interest rate on debt | 6.25% | 6.25% |  |  |  |  |
4.25% Senior Notes due December 2042 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 200,000,000 |  |  |  | 199,000,000 |  |
Interest rate on debt | 4.25% | 4.25% |  |  |  |  |
4.45% Senior Notes due May 2043 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 247,000,000 |  |  |  | 246,000,000 |  |
Interest rate on debt | 4.45% | 4.45% |  |  |  |  |
4.60% Senior Notes due June 2044 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 544,000,000 |  |  |  | 544,000,000 |  |
Interest rate on debt | 4.60% | 4.60% |  |  |  |  |
4.75% Senior Notes due May 2045 | Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 593,000,000 |  |  |  | 593,000,000 |  |
Interest rate on debt | 4.75% | 4.75% |  |  |  |  |
Commercial paper |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Total debt | $ 0 |  |  |  | $ 112,000,000 |  |

X
- Definition Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Represents the aggregate of total long-term debt, including current maturities and short-term debt. + References No definition available. + Details
Name: | us-gaap_DebtLongtermAndShorttermCombinedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_NotesPayableOtherPayablesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_FivePointZeroZeroPercentSeniorNotesDueTwentyTwentyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_TwoPointEightZeroPercentSeniorNotesDueTwentyTwentyOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A2.20SeniorNotesdueNovember2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A4.00SeniorNotesDueNovember2023Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A3.50NotesdueJune2024Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A3.875SeniorNotesdueDecember2025Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A2.875notesdue2026Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_JuniorSubordinatedDeferrableInterestDebentures8.205PercentDue2027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A4.50SeniorNotesDueDecember2028Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A3.75SeniorNotesDueMay22029Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A280SeniorNotesDueMay2030Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_SeniorNotes625PercentDue2040Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_SeniorNotes4.25PercentDue2042Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_NotesDueat2043at4.45PercentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_A4.60SeniorNotesDueJune2044Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=aon_FourPointSevenFivePercentSeniorNotesDueTwentyFortyFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortTermDebtTypeAxis=us-gaap_CommercialPaperMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |