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Pension and Non-pension Post-employment Benefit Plans - Additional Information (Details) £ in Millions, $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2018 USD ($) | Jun. 30, 2018 GBP (£) | Sep. 30, 2020 USD ($) | Jun. 30, 2018 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Disclosure of defined benefit plans [line items] |  |  |  |  |  |  |
Percentage of plan members that are active employees of the Company |  |  |  |  | 1.00% |  |
Gain (Loss) on Purchase of Annuity Recognised in Profit Or Loss |  |  |  | $ 63.3 | $ 0.0 | $ 4.1 | $ 0.0
Loss on pension annuity purchases (note 19(a)) |  |  | $ 0.2 |  | 0.2 | 0.0 | $ 63.3
Plan assets, at fair value |  |  |  |  | $ 380.1 | 330.3 |
Percentage of plan assets held with financial institutions with a rating of A- or above |  |  |  |  | 97.00% |  |
Number of basis points |  |  |  |  | 1.00% |  |
UK Main Pension Plan |  |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |  |
Cost of annuity purchased | $ 209.2 | £ 156.1 |  |  |  |  |
Level 1 |  |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |  |
Plan assets, at fair value |  |  |  |  | $ 31.8 | 30.5 |
Level 3 |  |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |  |
Plan assets, at fair value |  |  |  |  | $ 348.3 | $ 299.8 |

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- Definition Number of Participants Of Retirement Benefit Plan Receiving Benefits, Percentage + References No definition available. + Details
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- Definition Percentage Of Plan Assets Held With Financial Institutions With A Rating Of A- Or Above + References No definition available. + Details
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- Definition The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2020-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_57_a&doctype=Standard -URIDate 2020-01-01 + Details
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