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Claims, Lawsuits, and Other Contingencies - Legal Narrative (Details) £ in Millions, $ in Millions |  |  |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2021 USD ($) | Sep. 06, 2018 USD ($) | Oct. 03, 2017 NZD ($) | Apr. 30, 2021 USD ($) plaintiff | Apr. 30, 2021 GBP (£) plaintiff | Aug. 31, 2020 USD ($) plaintiff | Nov. 30, 2019 USD ($) defendant | Nov. 30, 2018 USD ($) | Dec. 31, 2016 USD ($) | Sep. 16, 2020 USD ($) | Apr. 27, 2018 USD ($)
Aviation and Aerospace Broking Industry |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total revenue |  |  |  |  |  |  |  |  | $ 100,000,000 |  |
Aon Hewitt Investment Consulting, Inc. |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Investment losses suffered by plaintiff |  |  |  |  |  |  |  |  |  |  | $ 200,000,000
Pending Litigation | Christchurch City Council |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Value of damages sought | $ 218,000,000 |  | $ 320 |  |  |  |  |  |  |  |
Pending Litigation | Fatal Plain Crash In November2016 |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  | $ 39,000,000 | £ 29 | $ 844,000,000 |  | $ 16,000,000 |  |  |
Loss contingency, number of defendants | defendant |  |  |  |  |  |  | 3 |  |  |  |
Damages sought option 1 |  |  |  |  |  |  | $ 300,000,000 |  |  |  |
Damages sought option 2 |  |  |  |  |  |  | 50,000,000 |  |  |  |
Damages sought option 3 |  |  |  |  |  |  | $ 25,000,000 |  |  |  |
Loss contingency, number of plaintiffs | plaintiff |  |  |  | 16 | 16 | 43 |  |  |  |  |
Pending Litigation | N E B C |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Investment losses suffered by plaintiff |  |  |  |  |  |  |  |  |  | $ 2,000,000,000 |
Minimum |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss | 0 |  |  |  |  |  |  |  |  |  |
Minimum | Pilkington North America, Inc. |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  | $ 45,000,000 |  |  |  |  |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss | $ 800,000,000 |  |  |  |  |  |  |  |  |  |
Maximum | Pilkington North America, Inc. |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  | 85,000,000 |  |  |  |  |  |  |  |  |
Damages awarded |  | $ 15,000,000 |  |  |  |  |  |  |  |  |

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