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Debt - Additional Information (Detail) - Multi Currency Revolving Credit Agreement [Member] - USD ($)
9 Months Ended
Sep. 30, 2020
Dec. 31, 2019
Debt Instrument [Line Items]    
Revolving credit agreement $ 350,000,000  
Credit agreement secured date Jan. 30, 2023  
Letters of Credit Outstanding $ 5,280,000  
Debt Outstanding 0  
Unused Revolving credit 344,720,000  
Unrestricted retained earnings $ 351,219,000 $ 283,956,000