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Long-Term Debt and Financing Arrangements - Additional Information (Detail) - USD ($)
9 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Revolving Line of Credit Facility [Member]    
Line Of Credit Facility [Line Items]    
Line of credit facility, maximum borrowing capacity $ 350,000,000  
Revolving Line of Credit Facility [Member] | Bank Revolving Line of Credit [Member]    
Line Of Credit Facility [Line Items]    
Borrowings under bank revolving line of credit 0  
Unused and available borrowings under bank revolving line of credit 319,400,000 $ 323,000,000.0
Standby Letters of Credit [Member]    
Line Of Credit Facility [Line Items]    
Outstanding letters of credit $ 30,600,000  
Standby Letters of Credit [Member] | Minimum [Member]    
Line Of Credit Facility [Line Items]    
Letters of credit expiration year 2019  
Standby Letters of Credit [Member] | Maximum [Member]    
Line Of Credit Facility [Line Items]    
Letters of credit expiration year 2020