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Savings Plan - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Savings Plan [Line Items] |  |  |
Savings plan maximum percentage of employees contribution allowable | 20.00% |  |
Percentage of employer contributions vested per year | 25.00% |  |
Maximum employment period considered for vesting of employers' contribution, in years | 4 years |  |
Liability, Retirement and Postemployment Benefits | $ 38.0 | $ 32.7 |
U.S. Qualified Pension Plan |  |  |
Savings Plan [Line Items] |  |  |
Maximum percentage of matching contributions made by the employer | 100.00% | 100.00% | 100.00%
Percentage of employer match on employee contribution | 4.00% | 4.00% | 4.00%
Savings Plan |  |  |
Savings Plan [Line Items] |  |  |
Amounts charged to statements of operations | $ 21.7 | $ 20.9 | $ 19.4

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