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Short-Term Borrowing - Additional Information (Detail)
1 Months Ended 3 Months Ended 12 Months Ended
Feb. 28, 2021
USD ($)
Dec. 31, 2021
USD ($)
Dec. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
Short-term Debt [Line Items]        
Short-term borrowings   $ 221,634,000 $ 221,634,000 $ 175,644,000
Line of Credit Facility, Aggregate Borrowing Capacity   $ 200,000,000 $ 200,000,000  
Number Of Unsecured Bank Credit Facilities     3  
Short-term Debt, Weighted Average Interest Rate, at Point in Time   0.83% 0.83% 1.28%
Ratio of Indebtedness to Net Capital   0.65 0.65  
Long-term debt including current maturities   $ 568,800,000 $ 568,800,000 $ 523,000,000
Line of Credit Facility, Commitment Fee Percentage     95.00%  
Line of Credit Facility, Remaining Borrowing Capacity   173,100,000 $ 173,100,000  
Letters of Credit Outstanding, Amount   5,300,000 5,300,000  
Notional Amount of Nonderivative Instruments   60,000,000 30,000,000 $ 100,000,000
Financing Receivable, Revolving   400,000,000 400,000,000  
Subsequent Event        
Short-term Debt [Line Items]        
Notional Amount of Nonderivative Instruments $ 40,000,000      
Fixed Swap Rate 0.17%      
Revolving Credit Facility [Member]        
Short-term Debt [Line Items]        
Line of Credit Facility, Aggregate Borrowing Capacity   $ 400,000,000 $ 400,000,000  
Committed Line of Credit Facility Two [Member]        
Short-term Debt [Line Items]        
Debt Instrument, Description of Variable Rate Basis     LIBOR rate, plus 0.75 percent  
Committed Line of Credit Facility Three [Member]        
Short-term Debt [Line Items]        
Debt Instrument, Description of Variable Rate Basis     Lender's base rate, plus 0.75 percent  
Interest Rate Swap Rate, Low Range [Member]        
Short-term Debt [Line Items]        
Fixed Swap Rate   0.20% 0.2615%  
Interest Rate Swap Rate, High Range [Member]        
Short-term Debt [Line Items]        
Fixed Swap Rate   0.205% 0.3875%  
Revolving Line of Credit, Short-term        
Short-term Debt [Line Items]        
Financing Receivable, Revolving   $ 200,000,000 $ 200,000,000  
Debt Instrument, Interest Rate, Stated Percentage   70.00% 70.00%  
Revolving Line of Credit, Long-term        
Short-term Debt [Line Items]        
Debt Instrument, Fee     0.09