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Debt - Additional Information (Detail)
Jun. 17, 2020
USD ($)
Jun. 29, 2018
USD ($)
Financial_Institution
Apr. 30, 2020
USD ($)
Line of Credit Facility [Line Items]      
Line of credit outstanding     $ 220,000,000
Subsequent Event      
Line of Credit Facility [Line Items]      
Repaid of borrowing $ 100,000,000    
Stand-by letters of credit      
Line of Credit Facility [Line Items]      
Letter of credit outstanding     14,499,000
Trade Letter of Credit      
Line of Credit Facility [Line Items]      
Letter of credit outstanding     55,240,000
Number of financial institutions with borrowing agreements | Financial_Institution   2  
Line of credit facility available for purposes of trade of letter of credit   $ 130,000,000  
Line of credit facility, available amount     $ 74,760,000
JPMorgan Chase Bank N. A. | Revolving Credit Facility      
Line of Credit Facility [Line Items]      
Credit agreement initiation date   Jun. 29, 2018  
Credit facility maturity date   2023-06  
Credit facility maximum borrowing capacity   $ 350,000,000  
Additional line of credit facility   $ 150,000,000  
Commitment fee percentage   0.20%  
JPMorgan Chase Bank N. A. | Revolving Credit Facility | Adjusted LIBOR, CDOR or EURIBOR | Minimum      
Line of Credit Facility [Line Items]      
Applicable margin   1.125%  
JPMorgan Chase Bank N. A. | Revolving Credit Facility | Adjusted LIBOR, CDOR or EURIBOR | Maximum      
Line of Credit Facility [Line Items]      
Applicable margin   1.375%  
JPMorgan Chase Bank N. A. | Revolving Credit Facility | Adjusted ABR | Minimum      
Line of Credit Facility [Line Items]      
Applicable margin   0.125%  
JPMorgan Chase Bank N. A. | Revolving Credit Facility | Adjusted ABR | Maximum      
Line of Credit Facility [Line Items]      
Applicable margin   0.375%