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Pension and Post-Employment Benefits - Defined Benefit Pension Plan (Detail) - United Kingdom Plan [Member] - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Plan assumptions at December 31, (%): |  |  |
Discount rate | 2.78% | 2.56% | 2.48%
Inflation rate | 2.25% | 2.20% | 2.25%
Rate of return on plan assets - overall on bid-value | 3.05% | 2.75% | 3.20%
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 100.00% | 100.00% | 100.00%
Equity Securities [Member] |  |  |
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 12.00% | 38.00% | 25.00%
Debt Security [Member] |  |  |
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 83.00% | 53.00% | 66.00%
Cash [Member] |  |  |
Plan asset allocation by category (%): |  |  |
Total plan asset allocation by category | 5.00% | 9.00% | 9.00%
United Kingdom [Member] |  |  |
Plan net pension (credit)/charge: |  |  |
Interest cost on PBO | $ 15.0 | $ 15.2 | $ 20.8
Expected return on plan assets | (22.2) | (24.5) | (29.9)
Amortization of prior service credit | (1.1) | (1.0) | (1.1)
Amortization of actuarial net losses | 2.0 | 5.0 | 2.6
Plan net pension (credit)/charge | $ (6.3) | $ (5.3) | $ (7.6)

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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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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