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Financial Guarantees (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Financial Guarantees [Line Items]    
Term of standby letters of credit, years 1 year  
Notional amount of standby letters of credit $ 86,900,000 $ 87,800,000
Carrying value of letters of credit 500,000 600,000
Notional amounts 1,452,000,000 $ 665,500,000
Interest Rate Swap    
Financial Guarantees [Line Items]    
Notional amounts $ 54,300,000