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Pension and Post-Employment Benefits - Unfunded Defined Benefit Pension Plan (Detail) - German Plan [Member] - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Plan net pension charge: |  |  |
Interest cost on PBO | $ 0.1 | $ 0.2 | $ 0.2
Amortization of actuarial net loss | 0.8 | 0.3 | 0.4
Plan net pension (credit)/charge | $ 0.9 | $ 0.5 | $ 0.6
Plan assumptions at December 31, (%): |  |  |
Discount rate | 0.40% | 0.80% | 1.90%
Inflation rate | 1.50% | 1.75% | 1.75%
Rate of increase in compensation levels | 2.75% | 2.75% | 2.75%

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