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Pension and Post-Employment Benefits - Defined Benefit Pension Plan (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Plan net pension (credit)/charge: |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] | Other Nonoperating Income (Expense) | Other Nonoperating Income (Expense) | Other Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Other Nonoperating Income (Expense) | Other Nonoperating Income (Expense) | Other Nonoperating Income (Expense)
United Kingdom Plan [Member] |  |  |
Plan assumptions at December 31, (%): |  |  |
Discount rate | 4.59% | 4.91% | 1.84%
Inflation rate | 2.70% | 2.85% | 3.55%
Rate of return on plan assets - overall on bid-value | 4.25% | 4.00% | 2.30%
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 100.00% | 100.00% | 100.00%
United Kingdom Plan [Member] | Cash [Member] |  |  |
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 4.00% | 4.00% | 13.00%
United Kingdom Plan [Member] | Defined Benefit Plan Debt Securities And Insurance Contracts [Member] |  |  |
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 96.00% | 96.00% | 82.00%
United Kingdom Plan [Member] | Defined Benefit Plan Equity Securities And Real Estate [Member] |  |  |
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 0.00% | 0.00% | 5.00%
United Kingdom [Member] |  |  |
Plan net pension (credit)/charge: |  |  |
Service cost | $ 3.3 |  |
Interest cost on PBO | 18.5 |  |
Expected return on plan assets | (25.7) |  |
Amortization of prior service cost/(credit) | 0.5 |  |
Amortization of actuarial net losses | 0.0 |  |
United Kingdom [Member] | United Kingdom Plan [Member] |  |  |
Plan net pension (credit)/charge: |  |  |
Service cost | 3.4 | $ 2.2 | $ 1.6
Interest cost on PBO | 19.6 | 10.1 | 7.6
Expected return on plan assets | (25.2) | (16.0) | (15.5)
Amortization of prior service cost/(credit) | 0.5 | 0.5 | 0.3
Amortization of actuarial net losses | (1.6) | 0.0 | 1.6
Settlement event | 0.0 | 0.0 | (0.3)
Net periodic cost/(benefit) | $ (3.3) | $ (3.2) | $ (4.7)

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-6 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-6 + Details
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